Processing method using both a remotely generated plasma and an in-situ plasma with UV irradiation

ABSTRACT

A processing apparatus and method wherein a wafer is exposed to activated species generated by a first plasma which is separate from the wafer, but is in the process gas flow stream upstream of the wafer, and is also exposed to plasma bombardment generated by a second plasma which has a dark space which substantially adjoins the surface of the wafer. The in situ plasma is relatively low-power, so that the remote plasma can generate activated species, and therefore the in situ plasma power level can be adjusted to optimize the plasma bombardment. Ultraviolet light to illuminate the face of a wafer being processed is generated by a plasma which is within the vacuum chamber but is remote from the face of the wafer. It is useful to design the gas flow system such that the ultraviolet-generating plasma has its own gas feed, and the reaction products from the ultraviolet-generating plasma do not substantially flow or diffuse to the wafer face. A transparent isolator is usefully included between the ultraviolet plasma space and the processing space near the wafer face, so that the ultraviolet plasma can be operated at a vacuum level slightly different from that used near the wafer face, delete but this transparent window is not made thick enough to act as a full vacuum seal.

This is a division of application Ser. No. 07/282,917, filed Dec. 5,1988 now U.S. Pat. No. 5,138,973, which is a continuation of 07/074,456filed July. 16, 1987 (now abandoned).

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to apparatus and methods for manufacturingintegrated circuits and other electronic devices.

One of the basic problems in integrated circuit manufacturing is defectscaused by the presence of particulates. For example, if photolithographywith 0.8 micron minimum geometry is being performed to pattern aconductor layer, the presence of a 0.5 micron particle can narrow thepatterned line enough to cause a defect which will prevent the circuitfrom operating (either immediately due to an open circuit, or eventuallydue to electromigration). For another example, if a 100 Å particle ofsilicon adheres to the surface and is included in a 200 Å nitride layerbeing grown, the dielectric will have greater chances of breaking downat that point, even assuming that no subsequent process step disturbsthe silicon particle.

This problem is becoming more and more troublesome because of two trendsin integrated circuit processing: First, as device dimensions becomesmaller and smaller, the size of a "killing defect" becomes smaller, sothat it is necessary to avoid the presence of smaller and smallerparticles. This makes the job of making sure that a clean room is reallyclean increasingly difficult. For example, a clean room which is Class 1(i.e. has an atmosphere with less than one particle per cubic foot) forparticles of one micron and larger may well be Class 1000 or worse ifparticle sizes down to 100 Angstroms are counted.

Second, there is an increased desire to use large size integratedcircuits. For example, integrated circuit sizes larger than 50,000square mils are much more commonly used now than they were five yearsago. This means that each fatal defect is likely to destroy a largerarea of processed wafer than was previously true. Another way to thinkof this is that not only has the critical defect size decreased, but thecritical defect density has also decreased.

Thus, particulates are not only an extremely important source of loss inintegrated circuit manufacturing yields, but their importance willincrease very rapidly in the coming years. Thus, it is an object of thepresent invention to provide generally applicable methods forfabricating integrated circuits which reduce the sensitivity of theprocess to particulate contamination.

One of the major sources of particulate contamination ishuman-generated, including both the particles which are released byhuman bodies and the particles which are stirred up by equipmentoperators moving around inside a semiconductor processing facility(front end). To reduce the potential for particulate contamination fromthis major source, the general trend in the industry has been to makemore use of automatic transfer operations. Using such operations, forexample, a cassette of wafers can be placed into a machine, and then themachine automatically transfers the wafers, one by one, from thecassette through the machine (to effect the processing steps necessary)and back to the cassette, without manual assistance.

However, efforts in the area of automatic transfer operations haveserved to highlight the importance of a second source of particles,namely particles generated by the wafers and the transfer mechanismsduring handling and transport operations. When the surface of the waferjostles slightly against any other hard surface, some particulate (ofsilicon, silicon dioxide, or other materials) is likely to be released.The particulate density inside a conventional wafer carrier is typicallyquite high, due to this source of particulate. Moreover, many of theprior art mechanisms for wafer transport generate substantial quantitiesof particulate. The general problem is discussed in U.S. Pat. Nos.4,439,243 and 4,439,244, which are incorporated by reference hereinto.

Some types of wafer processing are shown in U.S. Pat. Nos. 4,293,249 byWhelan issued on Oct. 6, 1981, 4,306,292 by Head issued on Dec. 15,1981, and 3,765,763 by Nygaard issued on Oct. 16, 1973, which areincorporated by reference hereinto.

The prior applications of common assignee discussed above addressed thisfacet of the problem by providing a vacuum wafer carrier in whichparticulate generation due to abrasion of the surface of the waferduring transport is reduced. The teachings of these prior applicationsenabled not only reduced generation of particulate in the carrier duringtransport and storage, but also reduced transport of particulate to thewafer's active face during transport and storage, by carrying the wafersface down under a high vacuum. This allowed the rapid settling of bothambient and transport generated particulate on other than the activewafer face.

The wafers can therefore be transported, loaded, unloaded and processedwithout ever seeing atmospheric or even low vacuum conditions. This isextremely useful, because, at pressures of less than about 10⁻⁵ Torr.there will not be enough Brownian motion to support particles of sizeslarger than about 100 Å, and these particles will fall out of thislow-pressure atmosphere relatively rapidly.

FIG. 2 shows the time required for particles of different sizes to fallone meter under atmospheric pressure. Note that, a pressure of 10⁻⁵ Torror less, even 100 Å particles will fall one meter per second, and largerparticles will fall faster. (Large particles will simply fallballistically, at the acceleration of gravity.) Thus, an atmosphere witha pressure below 10⁻⁵ Torr means that particles one hundred angstroms orlarger can only be transported ballistically, and are not likely to betransported onto the critical wafer surface by random air currents orBrownian drift.

The relevance of this curve to the various embodiments described in thepresent application is that the prior applications were the first knownteachings of a way to process wafers so that the wafers are neverexposed to airborne particulates, from the time they are loaded into thefirst vacuum process station (which might well be a scrubbing andpumpdown station) until the time when processing has been completed,except where the processing step itself requires higher pressures (e.g.for conventional photolithography stations or for wet processing steps).This means that the total possibilities for particulate collection onthe wafers are vastly reduced.

The prior applications cited above also taught use of the vacuum wafercarrier design together with a load lock and vacuum wafer transportmechanism at more than one process module, to provide a completelow-particulate wafer transfer system. These vacuum load locks canusefully incorporate mechanisms for opening a vacuum wafer carrier afterthe load lock has been pumped down, for removing wafers from the carrierin whatever random-access order is desired, and for passing the wafersone by one through a port into an adjacent processing chamber. Moreover,the load lock mechanism can close and reseal the vacuum wafer carrier,so that the load lock itself can be brought up to atmospheric pressureand the vacuum wafer carrier removed, without ever breaking the vacuumin the vacuum wafer carrier. This process takes maximum advantage of thesettling phenomena illustrated in FIG. 2 and described in more detailbelow. The wafer can then be moved in a virtually particulate freeenvironment from the carrier to the load lock, into the process chamberand back through the load lock to the carrier for, potentially, anentire manufacturing sequence.

A process station (which may optionally contain one process module ormore than one process module) has more than one load lock attached toit. This has several actual and potential advantages. First, processingcan continue on wafers transferred in from one load lock while the otherload lock is being reloaded, so that throughput is increased. Second,with some types of mechanical malfunction it will be possible to move atleast the in-process wafers out of the central module area (into one ofthe load locks, or even into one of the process modules) to keep themfrom exposure to ambient if it is necessary to vent the process moduleto correct the malfunction. This means that even fairly severe faultsmay be recoverable. Third, if separate transfer arms are provided insideeach of the load locks, this provides the further advantage that, if amechanical problem occurs with one transfer apparatus inside its loadlock, the process station can continue in production, using transferthrough the other load lock, while maintenance is summoned to correctthe mechanical malfunction.

The various process modules disclosed in the present application providea tremendous improvement in the modularity of processing equipment. Thatis, a reactor can be changed to any one of a very wide variety offunctions by a relatively simple replacement. It may be seen from thedetailed descriptions below that most of the different functionsavailable can be installed merely by making replacements in the wafersusceptor and related structures--i.e. in the top piece of the reactor,which bolts on--or in the feed structures. i.e. the structures directlybelow the wafer. Thus, the basic configuration of the vacuum chamber andwafer transfer interface is changed very little.

This capability confers tremendous advantages. First, the marginalcapital cost of adding a new processing capability is greatly decreased.Second, the flexibility of manufacturing space is greatly increased,since machines can be reconfigured with relative ease to perform newfunctions. Third, the design development time for reactor structures isgreatly decreased. Fouth, the time required to train personnel in use ofa new reactor is also greatly decreased, since many key functions willbe performed identically across a wide variety of reactors. Fifth, thecost of mistakes will be reduced, since operators will less frequentlymake mistakes due to unfamiliarity or confusion due to variety ofequipment. Sixth, the carrying cost of an adequate spare parts inventorywill be reduced. Seventh, the delay cost of repair and maintenancefunctions can be reduced, since many such functions can be performedoff-line after an appropriate replacement module is swapped into theproduction reactor. Eighth, the presence of disused and obsoletemachines in manufacturing space can be minimized, because a machinewhich had been configured to perform an unneeded function can bereconfigured.

The various classes of modules disclosed herein provide the advantagethat the "footprint" required to emplace them is minimal. That is, ifone or more process modules like those described is located in a cleanroom, only a minimum of clean room floor space (which is very expensive)will be required.

The capability for transferring wafers from one process chamber toanother without breaking vacuum is enhanced by the modular compatibilityof the below described embodiments. In particular, one of the advantagesof modular processing units of the kind disclosed herein is that asingle process station may advantageously contain several processmodules like those described, so that wafers need not even go throughthe load lock to be transferred between two modules which are in acommon station.

One way to think about the advantages of the various module designsdiscussed below might be to consider that they provide a super-capablereactor, i.e. has more adaptation capability than can ever be used forany single process. Viewed in this light, it may also be seen that theirfeatures are advantageous in sequential processing. That is, it has beenrecognized as desirable to perform more than one process in the samechamber without removing the wafer. The reactor designs disclosed hereinare particularly advantageous in doing this, since the "excess"capability of the reactor design means that it is easier to configure itto perform two sequential steps.

Other and further advantages are set forth within and toward the end ofthe Description of the Preferred Embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to theaccompanying drawings, wherein:

FIG. 1 shows a sample embodiment of a load lock which is compatible withvacuum processing and transport of semiconductor integrated circuitwafers.

FIG. 2 shows a graph of the time required to fall through air at variouspressures for particulates of various sizes.

FIG. 3 shows a sample wafer transfer structure, in a process station.wherein the wafer is placed onto three pins by the transfer arm 28reaching through the inter-chamber transfer port 30 from the adjacentvacuum load lock chamber 12.

FIG. 4 shows a closer view of a sample embodiment of a multi-wafervacuum wafer carrier 10, docked onto the position registration platform18 inside a load lock like that of FIG. 1.

FIGS. 5A and 5B show a plan view of a sample process stations includingprocess modules and wafer transfer stages, and a load locks.

FIG. 6 shows a configuration for a process module, which can be used asone of the process modules inside the process station shown in FIGS. 5Aand 5B.

FIG. 7 shows the plasma reactor of FIG. 6 in the closed position, as itwould be during the actual etch process.

FIG. 8 shows a plan view of the reactor of FIG. 6.

FIG. 9 shows an improved version of the process module of FIG. 6, in asample embodiment which includes the capability for process enhancementby ultraviolet light generated in situ and also the capability is alsoprovided for providing activated species (generated by gas flows throughan additional plasma discharge which is remote from the wafer face) tothe wafer face. The module is shown in a process station which includesonly one module and one load lock, but can also be used in embodimentslike that of FIGS. 5A and 5B.

FIG. 10 shows a physical configuration for a process station which canbe used for implementing some of the embodiments described herein.

FIG. 11 shows a flow chart for a load lock control system which providesparticulate protection in a vacuum process system.

FIG. 12 is a detailed view of the structure to realize the capabilityfor process enhancement by ultraviolet light generated in situ, inembodiments such as that of FIG. 9.

FIG. 13 shows an alternative version of the structure of FIG. 12,without the isolator window which (in the embodiment of FIG. 12) helpsseparate the gas flows of the ultraviolet source plasma from the processgas flows near the wafer face.

FIG. 14 shows a further alternative version of the structure of FIG. 12,wherein the plasma which provides the ultraviolet source is generatedbetween electrodes which are approximately cylindrical, and whereincapability is also provided for providing activated species (generatedby gas flows through an additional plasma discharge which is remote fromthe wafer face) to the wafer face.

FIG. 15 shows an example of a structure which generates activatedspecies by gas flows through a plasma discharge which is remote from thewafer face, in embodiments like that of FIG. 14.

FIG. 16 shows an example of a module which provides the combinedcapabilities of plasma bombardment from a plasma in close proximity tothe wafer face, and provision of activated species from a remotedischarge, and illumination of the wafer face with intense ultravioletlight.

FIG. 17 shows an example of a process module which provides two separategas feed distributors, and which is particularly advantageous forchemical vapor deposition operations using two source species.

FIG. 18 shows a portion of a process module which permits rapid thermalprocessing to be performed with reduced risk of wafer damage, and FIGS.19A, 19B and 19C schematically show how the operation of the heat sourceof FIG. 18 can alter the distribution of heating across the wafer, andFIG. 20 shows sample plots of heating across a wafer diameter under theconditions of FIG. 19B and 19C.

FIGS. 21A and 21B show two structures for reducing conductive heattransfer between a wafer and a transparent vacuum window in rapidthermal processing embodiments, including sample gas flow connections tosupply a purge gas to the void between the wafer and the transparentvacuum wall, and FIG. 21C shows a third way to minimize this conductiveheat transfer, and FIG. 21D shows a sample vacuum seal which may be usedwith a transparent vacuum wall which is subject to wide temperaturevariations in a rapid thermal processing environment.

FIG. 22 shows another configuration of a heat source for rapid thermalprocessing, in which the overall width of the heat source is minimal.

FIG. 23 shows the details of a process module, which provides combinedcapabilities for high-temperature processing (and cleanup), plasmabombardment, and provision of remotely generated activated species tothe wafer face.

FIG. 24 shows a process module, which provides combined capabilities forhigh-temperature processing (and cleanup), plasma bombardment, provisionof remotely generated activated species to the wafer face, andillumination of the wafer face by intense ultraviolet light generated insitu.

FIGS. 25A and 25B show a process module with capability foredge-preferential processing (and specifically for photoresist bakeand/or edge bead removal).

FIG. 26A shows a process module which permits cleanup and sputterdeposition, and FIG. 26B and 26C show details of the module of FIG. 26A,including a system for wafer transport within the module.

FIG. 27 shows a process module, compatible with a vacuum processingsystem, wherein multiple wafers are simultaneously processed under highpressure (or optionally under low pressure).

FIG. 28 shows a sample embodiment of an ion implanter process modulewhich is compatible with a vacuum processing system.

FIGS. 29A through 29G are magnified sectional views of the inner wallsof process gas piping, in several sample embodiments which provideadvantages in a semiconductor process modules.

FIGS. 30A through 30E show a distributor structure, and show theimproved results achieved with this structure in a descum process.

FIG. 31 is a block diagram of a computer control system.

FIG. 32 shows a process module with remote and in situ plasma.

FIGS. 33 and 34 show load lock chamber adapted to transfer wafersbetween a vacuum carrier and ambient.

FIGS. 35 and 36, which are similar, respectively to FIGS. 33 and 34, aload lock chamber adapted to transfer wafers between a vacuum carrierand a transfer mechanism to a vacuum processing system.

FIGS. 37 through 40 show details of a vacuum processor which has tworings of lamps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides major new concepts in semiconductorprocess methods and apparatus. The presently preferred embodiments willnow be discussed in great detail, but it must be appreciated that theconcepts which are included in these embodiments could also be used inmany other embodiments, and the scope of the invention is not delimitedby the particular examples shown.

FIG. 1 shows a sample embodiment of a vacuum wafer carrier 10 inside avacuum load lock chamber 12. The vacuum wafer carrier 10 is also shown,in slightly greater detail, in FIG. 4.

The vacuum wafer carrier 10 is shown with its door 14 open. The door 14is mounted in a pivotal manner to one side (the left side as shown inFIGS. 1 and 4) of the main body of carrier 10 by, for example, hinges(not shown). The door 14 has a vacuum seal 13 (FIG. 4) where it mateswith the body of the vacuum wafer carrier, so that the interior ofvacuum wafer carrier 10 can be maintained for several days and possiblyfor several tens of days, without enough leakage to raise the internalpressure above 10⁻³ Torr, for example, while the exterior of carrier 10is subjected to the atmosphere.

The vacuum wafer carrier 10 is adapted to dock with a positionregistration platform 18. The position registration platform 18 is onlypartially visible in FIG. 1, but is shown in more detail in FIG. 4. Whena vacuum wafer carrier 10 is placed inside the vacuum load lock chamber12, the position of the vacuum wafer carrier 10 will, therefore, beaccurately known. The vacuum wafer carrier 10 has ears 16 which engagevertical slots 17 fixed to the position registration platform 18. Thevacuum wafer carrier 10 can be slid into these slots until it rests onthe position registration platform 18, and thereby assure that theposition of the vacuum wafer carrier 10 is definitely known. It is alsouseful for the position registration platform 18 to include two taperedpins 21. As shown in FIG. 4, the pins 21 are both conical shaped butthey can be of different shapes, for example, one conical and onewedge-shaped. The pins 21 are positioned to engage tapered holes 23 inthe underside of the vacuum wafer carrier 10 when it is lowered withears 16 engaged with slots 17. A wide variety of other arrangementscould be used to assure mechanical registration. Thus, the use of slots17, ears 16, and pins 21 bring carrier 10 and chamber 12 into alignment(or mechanical registration).

The vacuum wafer carrier 10 also has a safety catch 15 which secures thedoor 14 from opening due to external forces being accidentally applied.An ear 500 extends from the side of the door 14 away from the hinges(not shown) which attach in to the main body of carrier 10. The safetycatch 15 can also be used to hold the door 14 closed if the carrier 10is used as a non-vacuum carrier. The ear is adapted to engage with asafety catch 15 rotatable mounted on the side (the right side as shownin FIG. 4) of carrier 10. However, under normal conditions of transport,this safety catch is not needed, since atmospheric pressure holds thedoor 14 shut against the internal vacuum of the vacuum wafer carrier 10.When the vacuum wafer carrier 10 is placed inside the vacuum load lockchamber 12 by engaging ears 16 with slots 17, a fixed finger 19 willengage the safety catch 15 and rotate it (upward as shown in FIG. 4)away from ear 500 to release it so that the door 14 can be opened. Fixedfinger 19 extends upward from platform 18 as shown in FIG. 4.

When the vacuum wafer carrier 10 is docked with the positionregistration platform 18, the door 14 will also be engaged with the topof door opening shaft 24. The door 14 can be provided with a shallowgroove (not shown) in its underside which mates with a finger and arm 25on the top of the door opening shaft 24. The arm 25 is located to engagethe door 14 near its attachment to the main body of carrier 10 in orderto rotate the door 14 as desired. Thus, after the load lock has beenpumped down so that differential pressure no longer holds the door 14closed the door can be opened by rotating (clockwise as shown in FIG. 4)door opening shaft 24. The door can be closed by rotating shaft 24counterclockwise as shown in FIG. 4.

After the vacuum wafer carrier 10 is placed in the vacuum load lockchamber 12 (FIG. 1) and closed the load lock lid 20 a purge (with drynitrogen or other clean gas) which can be at high pressure is usefullyapplied through the manifold 22 (FIG. 1) inside the load lock lid 20.The manifold 22 includes holes in lid 20, a connection with a source ofthe gas into the holes in lid 20, and openings from the holes in thebottom of lid 20. The gas flows from the source through the holes in lid20 and exits downward from lid 20 through the openings. The gas from themanifold 22 provides vertical flow which tends to transport particlesdownward. The gas flow from the manifold 22 also helps to remove some ofthe large particles which may have collected on the vacuum wafer carrier10 during its exposure to atmospheric conditions.

After this initial purge stage (e.g. for 30 seconds or more), thechamber is then slowly pumped down to 10⁻³ Torr or less. This stage ofthe pump down should be relatively slow, in order not to stir up randomparticulates. That is, while low pressures do permit particles to fallfrom the air, those particles will still be available on the bottom ofthe chamber, and must not be stirred up if this can be avoided.

In order to make sure that the airborne particulates have actuallyfallen out of the chamber air, the interior of the vacuum load lock canthen be allowed to stay at 10⁻³ or 10⁻⁴ Torr for a few seconds, to makesure that all of the particles which are able to fall out of the airwill do so.

The use of the carrier 10 and chamber 12 in the manner described abovegreatly reduce the problems of airborne particulates, which have alwaysbeen the dominant type of particulate transport, so that the problem ofballistically transported particulates can now be usefully addressed.

A sloped bottom and polished sidewalls for the load lock may be used asa modification of chamber 12. This would reduce the population ofparticulates sticking to the sidewalls and bottom which can be sentdisturbed by mechanical vibration.

Note that vacuum gauges 62 (FIG. 1) are connected to the interior of thevacuum load lock chamber 12. The vacuum gauges 62 include ahigh-pressure gauge (such as a thermocouple), a low pressure gauge (suchas an ionization gauge), and a differential sensor which accuratelysenses when the load lock interior pressure has been equalized with theatmosphere. The door of a vacuum wafer carrier 10 is not opened untilthese gauges indicate that desired vacuum has been achieved inside theload lock.

After a roughing pump and its isolation valve 702 (FIG. 31) has broughtthe chamber down to a soft vacuum, the gate or isolation valve 39 can beopened to connect the pump 38 to the interior of the load lock, and thepump 38 can then be operated to bring the pressure down to 10 to the -3Torr or less.

At this point, the pressures inside the vacuum wafer carrier 10 and thevacuum load lock chamber 12 are more or less equalized, and the door 14can be opened by activating by an door drive motor 26 (FIG. 4), which isconnected to door opening shaft 24 through a vacuum feedthrough 33.Motor 26 rotates shaft 24 in a clockwise direction as shown in FIGS. 1and 4 to open the door 14 and in a counterclockwise direction to closethe door 14. Two sensor switches 708 (FIG. 31) are also included insidethe vacuum load lock chamber 12, to ascertain when the door 14 is in itsfully opened position, and when the door 14 is fully shut. Thus, afterthe load lock chamber 12 has been pumped down and allowed to sit for afew seconds, the door opening shaft 24 is rotated in a clockwisedirection to open the door 14, until one sensor switch detects that thedoor is fully open.

During this time, the transfer arm 28 is kept in its home position at anelevation below the bottom of the door, so that the door 14 hasclearance to open. After the sensor switch detects that the door 14 isfully open, the transfer arm 28 can begin to operate. In order to closethe door 14, shaft 24 is rotated in a counterclockwise direction untilthe other sensor switch detects that the door 14 is closed.

The transfer arm 28 has two degrees of freedom. The arm is capable ofboth vertical and horizontal movement. One direction of motion permitsthe transfer arm 28 to reach into vacuum wafer carrier 10 or throughinterchamber transfer port 30 into the adjacent process module, forexample, process module 570 (FIG. 9). The other degree of freedomcorresponds to vertical motion of the transfer arm 28, which permitsselection of a wafer inside the vacuum wafer carrier 10 to remove, orwhich slot a wafer is placed into during a transfer operation.

An elevator drive motor 32 provides the elevation of the transfer arm28, and the arm drive motor 34 provides the extension and retraction ofthe transfer arm 28. Neither of these motors requires a vacuumfeedthrough since they are housed inside the exhaust manifold 36. Themanifold 36, as shown in FIG. 1. has a cylindrical shape and extendsfrom the bottom of chamber 12 downward. The manifold also extendsthrough and is attached to the bottom of chamber 12 a short distanceinto chamber 12. The pump 38 is at the end of manifold 36 away from itsattachment to chamber 12. The motor 26 also extends downward fromchamber 12. Pump 38 can be, for example, a turbomolecular pump. Theexhaust manifold 36 does not open directly into the vacuum load lockchamber 12, but instead has apertures 40 around its top (the end ofmanifold 36 extending into chamber 12). Thus, the exhaust manifold 36 isconfigured so that there is not a line of sight path from the elevatordrive motor 32, the arm drive motor 34, or from the pump 38 to thevacuum load lock chamber 12. This reduces ballistic transport ofparticulates from these moving elements into the load lock chamber. Thearrangement shown in FIG. 1 has been found useful but other arrangementsare possible to provide the necessary transportation of the wafer 48.

The elevator drive motor 32 is connected to drive a sub-platform 42 upand down, and the arm drive motor 34 is mounted on this sub-platform 42within the manifold 36. Motor 34 is fixed within manifold 36. The driveshaft of motor 32 drives a screw 510. Screw 510 passes through threadsin sub-platform 42 to drive sub-platform 42 up or down dependent on thedirection of rotation of the drive shaft of motor 32. Three rods 520,521, and 522 pass through and are capable of sliding engagement withsub-platform 42. The rods are affixed to the top of manifold 36. Alsoaffixed to sub-platform 42 is a tubular support 46. This linkage withinthe manifold 36 allows the transfer 28 to easily move vertically.

Another linkage is provided inside the rotatable transfer arm support 44which permits the transfer arm 28 to move very compactly. The tubularsupport 46 extends form sub-platform 42 up through the top of manifold36. The rotatable transfer arm support 44 is connected to to be drivenby a rotating rod (not shown) within tubular support 46. The tubularsupport 46 is fixed to arm support 44. Thus, the rotating rod is drivenby the arm drive motor 34 and in turn drives arm support 44 and therotatable transfer arm support 44 is mounted on a tubular support 46which does not rotate but moves up and down. An internal chain andsprocket linkage is used so that the joint between rotatable transferarm support 44 and transfer arm 28 moves with twice the angular velocityof the joint between rotatable transfer arm support 44 and tubularsupport 46. Of course, many other mechanical linkages couldalternatively be used to accomplish this. This means that, when therotatable transfer arm support 44 is in its home position, a wafer 48will be supported approximately above the tubular support 46, but whenthe rotatable transfer arm support 44 is rotated 90 degrees with respectto the tubular support 46, the transfer arm 28 will have been rotated180 degrees with respect to the rotatable transfer arm support 44, sothe transfer arm can either extend straight into the vacuum wafercarrier 10 or else straight through the inter-chamber transfer port 30into the adjacent processing chamber. This linkage is described ingreater detail in U.S. Pat. No. 4,659,413 issued to Davis et al on Apr.21, 1987, which is hereby incorporated by reference.

The transfer arm 28 is a thin piece of spring steel, e.g. 0.030 inchthick. The transfer arm 28 has 3 pins 50 (FIGS. 1 and 3) on it tosupport the wafer 48. Each of the 3 pins 50 includes a small cone 52(FIG. 3) on a small shoulder 1900 (FIG. 3). The small cones 52 and smallshoulders 1900 can be made of a material which is soft enough to notscratch silicon. For example, these portions, which are the onlyportions of transfer arm 28 which actually touch the wafers beingtransported, can be made of a high-temperature plastic (i.e. a plasticwith a relatively low propensity to outgas under vacuum) such as Ardel(a thermoplastic phenyl acrylate, made by Union Carbide) or Delrin. Notethat the use of a small cone 52 at the center of each of the 3 pins 50permits very slight misalignments of the wafer to the transfer arm 28 tobe corrected. In other words the system of wafer transport describedhere is a stable mechanical system, wherein small misalignments duringsuccessive operations will not accumulate, but will be damped out. Thecontact with the wafer 48 and the pins 50 are only at the edge of thewafer.

Note that, in the positioning of the wafer 48 as shown, one of the 3pins 50 rests against the flat portion 56 (FIG. 4) on the circumference49 (FIG. 4) of wafer 48. This means that, in this embodiment, the 3 pins50 on the transfer arm 28 do not define a circle of the same diameter asthe diameter of the wafer 48 to be handled.

To assure that the flat portion 56 (FIG. 4) of each wafer 48 does notinterfere with accurate handling of the wafers, the vacuum wafer carrier10 has a flat contact surface 29 on its interior back side which theflat portion 56 of each wafer 48 will rest against. Elastic elements 27(FIG. 4) on the inside surface of the door 14 pushes each wafer againstthis flat surface when the door 14 is closed, so that relative movementof the wafers and the carrier during transit is minimized, that is thewafers do not rub against the ledges 60. This also assures that, whenthe door 14 is opened, the location of the flat portion 56 on each wafer48 is accurately known. That is the wafer is in a known predeterminedalignment.

In operation, after the vacuum wafer carrier 10 is in the vacuum loadlock chamber 12 with its door 14 open, the elevator drive motor 32 isoperated to bring the transfer arm 28 to just below the height of thefirst wafer 48 which it is desired to remove, and the arm drive motor 34is then operated to extend the transfer arm 28 into the interior of thecarrier 10. This is the leftmost position of the three positions of arm28 shown in FIG. 1. By operating the elevator drive motor 32 briefly,the transfer arm 28 is raised slightly until the 3 pins 50 around itscircumference 49 lift the desired wafer off of the ledges 60 (FIG. 4) onwhich it has been resting inside the vacuum wafer carrier 10.

Note that the ledges 60, as shown in FIG. 4 are tapered surfaces ratherthan flat surfaces, so that contact between the ledges 60 and the wafer48 resting on them is a line contact rather than an area contact, and islimited to the edge of the wafer. This prevents contact between carrierand wafer over a substantial area, possibly of many square millimeters,but the "line contact" used is over a much smaller area, typically of afew square millimeters or less. An alternative definition of the "linecontact" used in this embodiment is that the wafer support contacts thesurface of the wafer only at points which are less than one millimeterfrom its edge. Thus, by raising the transfer arm 28, a wafer 48 will bepicked up, and will be resting on the small cones or small shoulders1900 of the 3 pins 50 on the transfer arm 28.

The ledges 60 can have a center-to-center spacing of 0.187 inches insidethe vacuum wafer carrier 10. This center-to-center spacing, less thethickness of the wafers 48, must allow clearance enough for the heightof the transfer arm 28 plus the 3 pins 50, but need not be much more.For example, the transfer arm is about 0.080 inch thick, including theheight of the small cones 52 on the 3 pins 50. The wafer 48 can be, forexample, about 0.021 inch thick so that about 0.085 inch clearance isavailable. The thickness and diameters of the wafers can vary widely.Generally, larger diameter wafers will have greater thicknesses, butvacuum wafer carrier 10 of this kind is suited to use with such largerdiameter wafers, since the size of the vacuum wafer carrier 10 and thecenter spacing of the ledges 60 inside the vacuum wafer carrier 10 cansimply be adjusted appropriately. The carrier 10 can also be adapted tocarry thinner wafers, for example, GaAs as desired.

After the transfer arm 28 has picked up the wafer 48, the arm drivemotor 34 is operated to bring the transfer arm 28 to the home position(which is the middle position as shown in FIG. 1). This is the middleposition of arm 28 as shown in FIG. 1. The elevator drive motor 32 isthen operated to bring the transfer arm 28 to a height where it canreach through the inter-chamber transfer port 30 (FIG. 3).

The inter-chamber transfer port 30 is covered by an isolation gate 31.Although the gate 31 as shown in FIG. 3 seals the inter-chamber transferport 30 by making sliding contact. When shaft 580 is rotated (as shownin FIG. 3), the linkage provided drives gate 31 upward (as shown in FIG.3) and covers the port 30. To open the port 30 the shaft 580 is rotatedin the opposite direction. If desired the sealing can be performed by arotated movement. (Again, the absence of sliding contact may beadvantageous to reduce internally generated particulates.) The isolationgate 31 over the inter-chamber transfer port 30 can operated by an aircylinder, but a stepper motor could be used in the alternative. Thus, atotal of four motors can be used: two which use vacuum feedthroughs, andtwo which are contained inside the exhaust manifold 36. The arm drivemotor is now operated again, to extend the transfer arm 28 throughinter-chamber transfer port 30 into the adjacent processing chamber.This is the rightmost position of arm 28 as shown in FIG. 1. Theadjacent processing chamber may be any one of many different kinds ofprocess modules, for example, any processing module disclosed hereinsuch as an implanter, a plasma etch, and a deposition module or anyother type of process module.

The transfer arm reaching through the inter-chamber transfer port 30will place the wafer 48 on wafer support pins 53 as shown in FIG. 3,like those used in the transfer arm 28 itself. (Note that theinter-chamber transfer port 30 should have enough vertical height topermit some vertical travel while the transfer arm 28 is extendedthrough inter-chamber transfer port 30, so that transfer arm 28 can movevertically to lift a wafer from or deposit a wafer onto the wafersupport, for example, wafer support pins 53 inside the processingchamber.) The wafer 28 is deposited by arm 28 on the tops of pins 53.

Alternatively, the processing chamber may include a fixture havingspaced sloped ledges like the ledges 60 inside the transfer box, or mayhave other mechanical arrangements to receive the wafer. However, in anycase, the arrangement used to receive the transferred wafer 48 must haveclearance on the underside of the wafer (at least at the time oftransfer), so that the transfer arm 28 can reach in on the underside ofthe wafer to emplace or remove it. If the wafer support pins 53 are usedto receive the transferred wafer, it may be desirable to provide abellows motion or a vacuum feedthrough in order to provide verticalmotion of the wafer support pins 53 inside the processing chamber. Thus,for example, where the processing chamber is a plasma etch or RIE(reactive ion etch) module, a bellows may be provided to move the wafer48 vertically, for example, onto a susceptor after the transfer arm 28has been withdrawn out of the way of the wafer 48.

Of course, the processing chamber may be an engineering inspectionmodule or deposition module, for example. A vacuum-isolated microscopeobjective lens will permit inspection of wafers in vacuum and (using anappropriately folded optical path) in a face-down position. This meansthat heavy use of engineer inspection can be made where appropriate,without the loss of engineer time and clean-room quality which can becaused by heavy traffic through a clean-room. The inspection modulecould be combined with other modules if desired.

In any case, the transfer arm 28 is withdrawn, and the gate 31 is movedto the closed position to close port 30, if desired. The process ofwafer 48 then proceeds. After processing is finished, the isolation gateover the interchamber transfer port 30 is opened again, the transfer arm28 is extended again, the elevator drive motor 32 is operated briefly sothat the transfer arm 28 picks up the wafer 48, and the arm drive motor34 is again operated to bring the transfer arm 28 back into the homeposition. The elevator drive motor 32 is then operated to bring thetransfer arm 28 to the correct height to align the wafer 48 with thedesired slot inside the vacuum wafer carrier. The arm drive motor 34 isthen operated to extend the transfer arm 28 into the vacuum wafercarrier 10, so that the wafer 48 which has just been processed issitting above its pair of ledges 60. The elevator drive motor 32 is thenbriefly operated to lower the transfer arm 28, so that the wafer isresting on its own ledges 60, and the arm drive motor 34 is thenoperated to retract the transfer arm 28 to home position. The sequenceof steps described above is then repeated, and the transfer arm 28selects another wafer for processing.

Note that, with the mechanical linkage of the transfer arm 28 androtatable transfer arm support 44 described above, the wafers beingtransferred will move in exactly a straight line if the center to centerlengths of transfer arm 28 and transfer arm support 44 are equal. Thisis advantageous because it means that the side of the wafer beingtransferred will not bump or scrape against the sides of the vacuumwafer carrier 10 when the wafer is being pulled out of or pushed intothe box. That is, the clearances of the vacuum wafer carrier 10 can berelatively small (which helps to reduce particulate generation byrattling of the wafers during transport in the carrier) without riskingparticulate generation due to abrasion of the wafers against the metalbox sides.

Processing continues in this fashion, wafer by wafer, until all thewafers inside the vacuum wafer carrier 10 (or at least as many of themas desired) have been processed. At that point the transfer arm 28 isreturned empty to its home position and lowered below the lower edge ofthe door 14, and the isolation gate 31 over inter-chamber transfer port30 is closed. Shaft 24 is rotated to close door 14 and provide initialcontact for the vacuum seals between door 14 and the flat front surfaceof vacuum wafer carrier 10, so that the vacuum wafer carrier 10 is readyto be sealed (by pressure differential) as the pressure inside the loadlock is increased. The vacuum load lock chamber 12 can now bepressurized again. When the differential sensor of the vacuum gauges 62determines that the pressure has come up to atmospheric, the load locklid 20 can be opened and the vacuum wafer carrier 10 (which is nowsealed by differential pressure) can be manually removed. A foldinghandle 11 is usefully provided on the top side of the carrier, to assistin this manual removal without substantially increasing the volumerequired for the vacuum wafer carrier 10 inside the load lock.

After the vacuum wafer carrier 10 has been removed, it can be carriedaround or stored as desired. The vacuum seal 13 will maintain a highvacuum in the vacuum wafer carrier 10 so that particulate transport tothe wafer surfaces (and also adsorption of vapor-phase contaminants) isminimized. The surface of wafers within the carrier 10 have the surfacewhich is being processed to construct devices are facing downward toprevent particulates from settling on that surface.

Note that the vacuum wafer carrier 10 also includes elastic elements 27mounted in its door. These elastic elements 27 exert light pressureagainst the wafers 48 when the door 14 is closed, and thus restrain themfrom rattling around and generating particulates. The elastic elements27 are configured as a set of springs in the embodiment shown, but othermechanical structures (e.g. a protruding bead of an elastic polymer)could alternatively be used to configure this. Where the wafers usedhave flats, a flat contact surface 29 is provided on the inner backsurface of the vacuum wafer carrier 10 for the wafer flats to be pressedagainst.

Note also that the ledges 60 on the sidewalls of the vacuum wafercarrier 10 are tapered. This helps to assure that contact with thesupported surface of the wafer is made over a line only, rather thanover any substantial area. This reduces wafer damage and particulategeneration during transport. This also assists in damping out theaccumulation of positioning errors, as discussed. The load lock lid 20can have a window (not shown), to permit inspection of any possiblemechanical jams.

An advantage of such embodiments is that, in the case of many possiblemechanical malfunctions, the door of the vacuum wafer carrier 10 can beclosed before attempts are made to correct the problem. For example, ifsomehow the transfer arm 28 picks up a wafer so that the wafer is notsitting properly on all three of the 3 pins 50, the door drive motor 26can be operated to close the door 14 before any attempts are made tocorrect the problem. Similarly, the inter-chamber transfer port 30 canbe closed if the transfer arm 28 can be retracted into home position. Itmay be possible to correct some such mechanical misalignment problemssimply by deviating from the normal control sequence. For example, theposition of a wafer 48 on the transfer arm 28 may in some cases beadjusted by partially extending the transfer arm 28, so that the edge ofthe wafer 48 just touches the outside of the door 14, or of theisolation gate over the inter-chamber transfer port 30. If this does notwork, the vacuum load lock chamber 12 can be brought back up toatmospheric pressure (with the door 14 of vacuum wafer carrier 10closed) and the load lid 20 opened so that the problem can be manuallycorrected.

FIGS. 6, 7, and 8 show a single wafer reactor which can be used forreactive ion etching. Many of the process modules described in thepresent application incorporate at least some of the ideas andadvantages of this embodiment, together with additional ideas andadditional advantages derived therefrom. (A very similar reactor designcan be used for plasma etching, i.e. etching at pressures higher than100 mTorr. The terms "plasmas etching" and "reactive ion etching" (or"RIE") are sometimes kept distinct in the art, with RIE being used torefer to etching under conditions where plasma bombardment is large,i.e. at lower pressure and with the wafer mounted on the poweredelectrode. This distinction will not be rigorously observed in thepresent application. The teachings of the present application areapplicable to both plasma and RIE etching as conventionallydistinguished, although some of the several features taught by thepresent application are more advantageous in the context of RIE etchingprocesses.

FIG. 6 shows a process module 104, which can be used in a processingsystem such as is shown in FIGS. 5A and 5B, as discussed below.

FIG. 6 shows a single wafer reactor which can be used for reactive ionetching or for plasma etching. As discussed above, the transfer arm 28places a wafer onto the wafer support pins 53 (FIG. 4) and thenretracts. At this point the whole lower assembly, including the chamber112, ground electrode 110, process gas distributor 120, base plate 138,and quartz cylinder 114 are moved upward. using. e.g.. an air cylinderor a vacuum feed through (not shown). A bellows 124 permits thisvertical motion to occur while maintaining a vacuum-tight interface tothe interior of the module 104. This vertical motion causes the backsideof the wafer resting on the wafer support pins 53 to make contact withthe powered electrode 118, and at this point the sliding pin supports130 which are attached to the underside of the wafer support pins 53retract slightly against a leaf spring 132. (Other elastic elementscould be used in place of leaf spring 132, to assure a small amount ofgive in the sliding pin supports 130, so that the wafer is not pressedagainst the powered electrode 118 with too much force.)

The last portion of the upward travel of this assembly causes the seal135 (FIG. 7) to make closure between the quartz cylinder 114 at the topof the chamber 112 and the quartz piece 116 which surrounds the poweredelectrode 118. Thus, when the seal is made, the interior of this processchamber is vacuum-sealed from the remainder of the interior of processmodule 104.

A helium bleed port 134 is provided to connect a helium supply to theback of the wafer. This helium space means that the space between thelow points of the powered electrode 118 and the wafer will be filledwith helium, rather than vacuum, and this assure a reasonablylow-thermal-resistance and highly repeatable thermal contact between thewafer and the powered electrode 118. The powered electrode 118 caninclude coolant manifold spaces 136, to which coolant can be supplied.

In an alternative embodiment, the pins 53 are not mounted on sliding pinsupports 130 supported by leaf spring 132, but are fixed. Since thehelium bleed port 134 assures good thermal contact between the back sideof the wafer and the surface of the powered electrode 118, a toleranceof several thousandths of an inch will still permit good RF coupling ofthe powered electrode 118 to the wafer 48, and still permit good thermalcontact between the powered electrode 118 and the wafer 48. A toleranceof this magnitude should provide enough allowance for thermal expansionsof chamber walls, variation in seal thickness, variation in waferthickness, etc., to still permit reliable sealing of the lower chamberportion to the upper portion. Note that, in this embodiment, the quartzcylinder 114 and quartz piece 116 would usefully be shaped slightlydifferently, to minimize the lateral spread of the plasma adjacent tothe face of the wafer. However, it has been found that utilizing slidingpin supports 130 permits the quartz cylinder 114 to confine the plasmaclosely near the wafer face 54 as shown in FIG. 7.

FIG. 7 shows the upper portion of the process module of FIG. 6, in theclosed position, with a wafer 48 held therein for processing. After thereactor has been closed, the helium bleed can be started through heliumbleed port 134 (FIG. 6). At the same time, desired process gases can beprovided through a process gas distributor 120.

The process gas distributor 120 is made of quartz, so that it does notpick up eddy currents from the RF power present. Moreover, since thesurface of the quartz is highly insulating, the plasma boundary near thequartz will not have as much voltage nor as much current across it asthe plasma boundary near a grounded conductive element would. This meansthat plasma-assisted reactions near the quartz will not occur at as higha rate as they would near a grounded conductive element, so thatdeposition is reduced. It should also be noted that quartz is a fairlygood thermal insulator, and the temperature of the susceptor maytherefore be raised (by radiation from the plasma) to 100 or 200 degreesC. This is advantageous for some processes, since raising thetemperature of the distributor will further reduce deposition on it.

Under typical RIE operating conditions (10 to 200 microns of pressure,and 100 to 800 watts of applied power) the generated plasma will fillthe chamber between the powered electrode 118 and the ground electrode110 fairly uniformly. Thus, the process gas distributor 120 protrudesinto the densest part of the plasma. The process gas distributor 120 isa ring, of perhaps one-half the diameter of the wafer being processed,with hollow supports which lead down to gas connections 140 (FIG. 6)mounted in the base plate 138. A quick-connect mounting is provided forthe quartz process gas distributor 120, so it can rapidly and easily bechanged out as desired.

The process gas distributor 120 is usefully spaced away from the surfaceof the wafer by only four centimeters, for example. This spacing, andthe exact shape of the process gas distributor 120, and the spacing ofthe gas feed ports 122 on the gas distributor, are not critical. Theseparameters can be changed if desired, but, if modified, they should beselected so that diffusion of process gases and process gas productsfrom the gas feed ports 122 in the process gas distributor 120provides: 1) diffusion-dominated transport of the process gases andprocess gas products to the plasma boundary at the face of the wafer 48;and 2) a fairly uniform concentration of process gases and process gasproducts at the plasma boundary next to the face of wafer 48. Forexample, the spacing of the process gas distributor 120 away from thewafer face could be anywhere in the range from one to fifteencentimeters.

Under these low pressure conditions, and given the high area ratiobetween the area of the powered electrode 118 in contact with the plasma(which, in this embodiment, is essentially the same as the area of wafer48), and the grounded electrode area (which in this embodiment isessentially the area of ground electrode 110, plus the interior area ofchamber 112 and the exposed upper area of base plate 138), a highdensity of plasma bombardment will occur at the face wafer face 54. Asis well-known to those skilled in the art, this plasma bombardmentassists in achieving desirable anisotropy effects during etching.

The ground electrode 110 can be cooled, using coolant lines 150 (FIG. 6)connected to manifold cavities inside the ground electrode 110. Ifadditional cooling is needed, the chamber 112 may also be cooled. Notethat coolant lines 150 are flexible hoses, to accommodate the verticaltravel of the whole lower etching chamber 138 as described above. Thegas supply tube 152, which supplies process gases through gasconnections 140 to the process gas distributor 120, is also flexible forthe same reason. If flexure of these hoses is found to generate excessparticulates, a gas feed outside the bellows 124, through the side ofthe base plate 138, could be used instead.

FIG. 8 shows a plan view of the reactor of FIG. 6. The shape of theprocess gas distributor 120 can be seen more clearly in this plan view.It can also be seen that the base plate 138 includes substantial spacesaround the edge of the ground electrode 110, which provide a passagefrom the gas feed ports 122 (FIG. 6) to a vacuum pump below. The overallgas flow in this reactor is downward, away from the face of the wafer,which assists in reducing particulates. An optional modification is theuse of an in situ vacuum particle counter in the chamber 112, so thatany increase in particle population in the critical volume can bedetected and the opening of chamber 112 delayed until the particle countreaches selected level.

After the desired etching operation is finished, the gas suppliedthrough process gas distributor 120 is cut off, and the process module104 is pumped down to the same pressure as the rest of the processmodule (10 to the -3 Torr or less). A holding time may then beinterposed, for thermal stabilization of the process module or forrelease of possible suspended particulates, and then the process module104 is opened and arm 28 operates as described above to remove the waferfrom chamber 12. The position of the arm 28 with the chamber 12 would bethe rightmost position of arm 28 shown in FIG. 1.

Note that all of the operations described above can be very easilycontrolled. No servos or complex negative feedback mechanisms areneeded. All the motors described are simple stepper motors, so thatmultiple modules of this type can be controlled by a single computercontrol system 206 FIG. 10). The mechanical stability of the system as awhole--i.e. the inherent correction of minor positioning errors providedby the tapering of the wafer support pins 53, by the slope of the ledges60 in the wafer carrier, and by the flat contact surface 29 on thebackwall of the vacuum wafer carrier 10--helps to prevent accumulationof minor errors, and facilitates easy control.

This advantage of simple control is achieved in part because goodcontrol of mechanical registration is achieved. As noted, the docking ofthe vacuum wafer carrier 10 with position registration platform 18provides one element of mechanical registration, since the location ofthe position registration platform 18 with respect to the transfer arm28 can be accurately and permanently calibrated. Similarly, the vacuumwafer carriers 10 do not need to be controlled on each dimension, butmerely need to be controlled so that the location and orientation of theledges 60 are accurately known with respect to the bottom (or otherportion) of the vacuum wafer carrier 10 which mates with positionregistration platform 18. As described above, this is accomplished byhaving channels which the vacuum wafer carrier 10 slides into until itrests on the position registration platform 18, but many othermechanical arrangements could be used instead. Various types ofelectronic and mechanical sensors could provide information about theposition and operation of the system for further control and correctiveaction by the computer control system 206.

Similarly, mechanical registration must be achieved between the homeposition of the transfer arm 28 and the 3 pins 50 (or other supportconfiguration) which the wafer will be docked to inside the processingchamber. However, this mechanical registration should be a simpleone-time setup calibration. Note that angular positioning will bepreserved by the vacuum wafer carrier itself, as was noted, whenever thedoor 14 is closed, spring elements inside it will press each wafer 48against the flat contact surface 29 of the vacuum wafer carrier 10.Optionally, the vacuum wafer carrier 10 could be provided with aquick-connect vacuum fitting, to permit separate pumpdown on the vacuumwafer carrier 10.

It should be noted that the load lock mechanism described need not beused solely with vacuum wafer carriers 10, although that has been couldto be useful. This load lock can also be used with wafer carriers whichcarry atmospheric pressure inside. Although this is an alternativeembodiment, it still carries substantial advantages, as is discussedabove, over prior art load lock operations such as that shown in U.S.Pat. No. 4,609,103, by Bimer et al. issued on Aug. 27, 1984, which isincorporated by reference hereinto.

It should be noted that a vacuum wafer carrier 10 as described can bemade in different sizes, to carry any desired number of wafers.Moreover, a vacuum wafer carrier 10 of this kind can be used to carry orstore any desired number of wafers, up to its maximum. This providesadditional flexibility in scheduling and process equipment logistics.

FIG. 5A shows a sample further alternative embodiment wherein two loadlocks, each containing a vacuum wafer carrier 10, are both connected toa process station 102 which contains four process modules one or more ofwhich can be a process module 104 or the other process modules disclosedherein or any other suitable module. Unlike the embodiment describedabove, when the transfer arm 28 reaches through the inter-chambertransfer port 30 from a vacuum load lock chamber 12 into the processstation 102, it places the wafer 48 onto one of two wafer stages 105.These wafer stages 105 can be three pin supports similar to pins 53 ortwo ledge supports, or may have other mechanical configurations as longas there is space underneath the supported wafer for the transfer arm 28to lower free of the wafer and retract after it has placed the wafer onthe supports. The wafer support used should be such as to make linecontact, rather than contact over any substantial area, with the undersurface or edge of the wafer.

Another transfer arm assembly 106 is provided inside the process station102. This transfer arm assembly is generally similar to the tansfer arm28, rotatable transfer arm support 44 and tubular support 46 as usedinside the chamber 12, but there are some differences. First, thetransfer arm 28 used inside the load lock only needs to move wafers in astraight line. By contrast, the transfer arm assembly 106 must also beable to move radially, to select any one of the process modules 104.Thus, an additional degree of freedom is needed. Second, the reach ofthe transfer arm assembly 106 need not be the same as the transfer arm28, the rotatable transfer arm support 44, and tubular support 46 usedinside the load lock, and in fact the reach of transfer arm assembly 106can be larger, to permit adequate spacing of the process modules 104.Third, the transfer arm assembly 106 does not need as much travel inelevation as the transfer arm 28 used in the load locks. Fourth, in theconfiguration shown, the transfer arm assembly 106 will not have one ofits 3 pins 50 resting on a wafer flat, so that the diameter of thecircle defined by 3 pins 50 is not the same for transfer arms 28 and128, even though they are handling wafers of the same diameter.

The tubular support of assembly 106 can be made rotatable and providinga third motor to drive this rotation. Thus, a third degree of freedomfor the transfer arm is provided. Similarly, the dimensions of thetransfer arm 128 of assembly 106 can simply be scaled as desired. Thus,transfer arm assembly 106 usefully includes a transfer arm rotatablymounted on a transfer arm support 144. The transfer arm support 144 ispivotably mounted to a tubular support (not shown), and an internalshaft, fixed to the transfer arm support 144, extends down through thetubular support. An internal chain drive with two to one gearingtranslates any differential rotation between tubular support 146 andtransfer arm support 144 into a further differential rotation, i.e.,over twice as many degrees between transfer arm support 144 and transferarm 128. An arm drive motor, mounted below the transfer arm assembly106, is connected to rotate the shaft which is fixed to transfer armsupport 144. An arm rotation motor is connected to rotate the tubularsupport 146. Finally, an elevator mechanism provides vertical motion ofthe transfer arm assembly 106.

Note that the vertical motion required of transfer arm assembly 106 isnot typically as much as that required of the transfer arm 28 in thevacuum load lock chamber 12, since the transfer arm 128 will typicallynot need to select one of several vertically separated wafer positionslike those in the vacuum wafer carrier 10, but will typically merely beused to pick and place wafers from a number of possible wafer moduleswhich are all in approximately the same plane. Thus, optionally thevertical elevation of the transfer 128 could be controlled by an aircylinder rather than by an elevator motor assembly as discussed above.

Thus, by rotating the tubular support of assembly 106 simultaneouslywith the transfer arm support 144, the transfer arm assembly 106 can berotated without being extended. After the transfer arm assembly 106 hasbeen rotated to the desired position, the tubular support 146 can beheld fixed while the transfer arm support 144 is rotated, and this willcause the transfer arm 128 to extend as described above in connectionwith arm 28.

Thus, after transfer arm 28 from one of the vacuum load lock chambers 12has placed a wafer 48 to be processed on one of the wafer stages 105.The transfer arm assembly 106 is rotated, if necessary, extended at alow position so that transfer arm 128 comes underneath the wafer,elevated so that transfer arm 128 picks up the wafer 48, and retractedto its home position. The transfer arm assembly 106 is then rotatedagain, and the transfer arm 128 is extended, so that the wafer is nowlocated above a wafer support in one of the process modules 104, orabove the other wafer stage 105. By lowering the transfer arm assembly106, the wafer 48 can now be placed on a wafer support within processmodules 104 or the wafer stage 105, and the transfer arm 128 can now beretracted.

The process module 104 can now be sealed off from the main processstation 102, and separate single-wafer processing of the wafer canbegin. Meanwhile, the transfer arms 128 and 28 can perform otheroperations. When a wafer in a process module 104 has completedprocessing, that process module 104 can then be pumped down to the samelow pressure as the interior of process station 102, and process module104 can be opened. The transfer arm assembly 106 can now be operated toremove this wafer, and transfer it either to one of the wafer stages 105or to another one of the process modules 104.

One advantage of such embodiments is that the process modules 104 canall be configured to do the same operation, which will permit wafertransport-limited throughput, even for fairly slow processingoperations, if there is a sufficient number of process modules 104 inthe process station 102; or, alternatively, different operations can beused in different ones of the process modules 104.

That is, such embodiments facilitate the use of sequential processing,which is increasingly recognized as desirable, since processingvariations caused by adsorbed contaminants or by native oxide areeliminated. For example, two of the process modules 104 can beconfigured for oxide growth, one for nitride deposition, and one forpolysilicon deposition, to permit complete in situ fabrication ofoxynitride poly-to-poly capacitors. Moreover, the provision of differentprocess steps in the different process modules 104 means that many lotsplits and process variations can be performed simply by programming theappropriate operations, without relying on manual identification ofwhich wafers should go to which machines. Thus, the capability to havedifferent operations proceed in different ones of the sample processmodules 104 provides additional processing flexibility.

Note also that the overall wafer transfer sequence is completelyarbitrary, and may be selected as desired. For example, the wafers fromone vacuum wafer carrier 10 could be completely processed and returnedto that vacuum wafer carrier 10, and the vacuum load lock chamber 12containing the just-processed wafers could be sealed off from processstation 102, so that the wafers in the other vacuum wafer carrier 10 inthe other vacuum load lock chamber 12 could be processed while thevacuum wafer carrier 10 full of processed wafers is removed from theother vacuum load lock chamber 12. Alternatively, the programmabilityand random access of this arrangement could be used to shuffle andinterchange wafers between the two vacuum wafer carriers 10 in whateverfashion desired.

It should also be noted that this arrangement is not at all limited totwo vacuum load lock chambers 12 nor to four process modules 104, butthe arrangement described can be scaled to other numbers of processmodules 104 in a station 102, or other numbers of vacuum load lockchambers 12 attached to a station 102, or to use of more than onetransfer arm assembly 106 inside a station, if desired.

Note that this arrangement still preserves wafer orientation. Assumingthat wafers are carried in vacuum wafer carrier 10 with their flatportion 56 toward flat contact on the back of carrier vacuum wafercarrier 10, they will be placed on wafer stage 105 with their flatportion 56 toward the center of station 102. Transfer arm assembly 106will preserve this orientation, so that, when the wafer 48 is replacedin either vacuum wafer carrier 10, it will have its flat portion 56toward the flat contact surface 29 on the back of the vacuum wafercarrier 10.

FIG. 5B shows a process station 550 which has three process modules 554which can be any of the process modules shown herein such as processmodule 104 or another appropriate process module. The process modules554 can be the same type of process module, each can be different, ortwo can be same and the other different. The transfer arm assembly 558,which is similar to transfer arm assembly 106 in FIG. 6, is adapted totransfer the wafer between any of the process modules 554 in any orderunder the control of the computer control system 562. The vacuum loadlock chambers 565 and 566 are similar to chamber 12 in FIG. 1. The arm558 can reach into modules 554 and chambers 565 and 566 to remove ordeliver wafers (only wafer 48 is shown in FIG. 5B. The computer controlsystem 562 supplies the necessary control for modules 554, assembly 558,and chambers 565 and 566. The routing of the wafers can be from anychamber 565 and 566 to any process module 554, between any desiredprocess modules 554, and from any process module 554 to any chamber 565and 566.

A closed loop particle control system is usefully provided to controlthe operation of the load lock and the process chamber before and afterprocessing operations in any of the chambers 565 and 566, as discussedabove in connection with chamber 12 FIG. 1).

FIG. 9 shows an improved version of the process module of FIG. 6. in anembodiment which includes the capability for process enhancement byultraviolet light generated in situ and the capability is also providedfor providing activated species, generated by gas flows through anadditional plasma discharge which is remote from the wafer face to thewafer face. The module is shown in a process station 570 which includesonly one module and one vacuum load lock, but can also be used inembodiments like that of FIGS. 5A and 5B, where a central handlingchamber is combined with plural process modules 104 and one or morevacuum load lock chambers 12.

Note that a particulate sensor 202 (FIG. 9) is explicitly shownconnected to the interior of the vacuum load lock chamber 12. Thisparticulate sensor 202 need not be physically located very close to thedocking position of vacuum wafer carrier 10, as long as the signal fromparticulate sensor 202 does provide an indication of the level ofparticulates present in the interior of the vacuum load lock chamber 12.The particulate sensor 202 is usefully located downstream from thevacuum load lock 12, in the pump out path (not shown). The particlesensor is a commercially available laser particle counter (which detectsindividual particles) combined with a counter which provides an outputsignal showing the number of particles counted over a certain timeduration. The ultraviolet plasma space 220 is supplied with a gas usefulfor the production of ultraviolet light, for example, H₂, Ar, or Hethrough ring 576. The frequency of the power utilized to generate theultraviolet light can be, for example, 100 KHz or 13.56 MHz. The module570 has a process chamber 218 which can have gas introduced througheither a distributor 212 or feed 250. Ozone, for example, could be feedthrough distributor 212. A transparent vacuum wall 238 allow the radiantheat from a heating module 572 to pass through to wafer 48 below.

The following process can also be used with FIG. 9 and the other processmodules which have ultraviolet light and remote plasma capability.

One process which can be used with module 570 is for the deposition ofpolysilicon utilizing either or both an additional ultraviolet generatedin side module 570 (which is directly optically coupled into the processchamber 218) and a remotely generated plasma from remote plasma chamber254. A silane gas is introduced into the process chamber. If the remoteplasma is not used then the silane gas can also be introduced intochamber 218 through distributor 212. The chamber should be maintained atdeposition temperature. After the wafer is disposed with chamber 218, apurge can be performed if desired by utilizing an appropriate gas whichis non-reactive with the wafer and the exposed layers thereon, forexample, N₂. An example of this process follows: The wafer is placed inthe chamber. The chamber is evacuated and purged with N₂ (in general thepressures usable within the chamber are between 0.1 to 750 Torr). Aremote plasma is generated within chamber 254 from silane gas. Theremote plasma is introduced into the chamber 218 and to the downwardfacing face 54 of wafer 48. The chamber is heated to the depositiontemperature of, for example, 550 to 700 degrees C. Additionalultraviolet energy is coupled into chamber 218 from space 220 byexciting the gas therein, for example, H₂, Ar, or He introduced throughring 576 using a power of 300 watts at a frequency of 100 KHz. Thereaction is as follows:

    SiH.sub.4 >SiH.sub.2 +Si.sub.2 H.sub.6 >Polysilicon +H.sub.2

where the light enhances deposition by increasing the molecularexcitation level. The gases and heat is turned off and the chamber isagain purged, with an appropriate gas, if desired. The wafer is thenremoved. A cleaning step can then be performed as desired utilizing aremote plasma formed from a mixture of HCl and HBr.

Another useful process is the deposition of silicon nitride. A source ofnitrogen is used to generate a remote plasma. Locally generatedultraviolet energy is coupled into the process chamber, as discussedabove. A gas mixture of a source of silicon, for example, dichlorosilane(DCS) is introduced into the process chamber and to the face 54 of thewafer. The remote plasma and the ultraviolet energy in combination allowthe deposition rate to be raised to an acceptable level. A sampleprocess follows:

1. Disposing the wafer into the process chamber face down and thechamber closed.

2. Evacuating the process chamber and then purging with an appropriategas, for example, N₂, if desired.

3. Generating a remote plasma from a gas mixture of DCS and a source ofnitrogen, for example, N₂ or NH₃, is introduced into the processchamber.

4. Heating the process chamber to the deposition temperature, forexample, between 550 and 800 degrees C.

5. Generating ultraviolet energy coupled into the process chamber whichis absorbed by the process gases to increase the molecular excitationlevel of the DCS.

6. Halting gas flows and heating and purging the chamber with anappropriate gas, for example, N₂.

7. Opening the process chamber and removing the wafer from the processchamber.

8. Cleaning the process chamber using a gas mixture of, for example, CF₄and O₂.

During the cleaning operations discussed herein the process chamber canbe closed.

The process module 570 is capable of sequentially removing organics,removing metallic contaminates, removing native oxides, oxidizing, thendepositing a shield over the oxide film formed. An example of such aprocess follows:

1. Disposing the wafer into the process chamber at low pressure.

2. Removing organic compounds from the wafer utilizing additionalultraviolet light and introducing ozone into the chamber.

3. Removing metallic contaminates using halides and oxygen:

4. Removing the native oxides caused by the prior steps utilizingFluorine chemistry, for example, anhydrous HF technique.

5. Evacuating and then purging the chamber to a higher pressure, forexample, 700 Torr, using an appropriate gas which is non-reactive withthe wafer and the exposed layers thereon, for example, N₂ or Ar.

6. Forming an oxide film on said wafer, or at least a part thereof, byintroducing an oxidizing source, for example, O₂, and heating the wafer,for example, by actuating lamps 574 of heating module 572 to provideradiant heat through wall 238.

7. Performing an anneal operation, for example, by turning off theoxidizing source and purging with N₂ or Ar, after the anneal operationturning off the heat and allowing the wafer to cool, if desired.

8. Remove the moisture, if desired, by utilizing a purge operation.

9. Evacuating the chamber and purging the chamber with an appropriategas, for example, N₂ or Ar to a lower pressure, for example, 750 to 0.1Torr.

10. Introducing a gas for deposition into the chamber, for example,silane to deposit polysilicon or Silicon Nitride could be utilized.

11. Heating the wafer to a deposition temperature, for example, 550 to700 degrees.

12. Generating additional ultraviolet light to increase the excitationlevel.

13. Removing the heat and deposition gas and purging the chamber with anappropriate gas, for example, N₂ or Ar and another deposition could besuch as Silicon Nitride.

14. After removing the wafer from the process chamber, utilizing remoteplasma to clean the chamber prior to the next wafer.

Various of the above steps and/or portions can be omitted if required bythe particular process.

Another process, which can be useful for the process module 570 of FIG.9, is the deposition of silicon dioxide. The wafer is placed into theprocess chamber. The chamber is evacuated and then purged, if desired,with an appropriate gas, for example, N₂. The pressure can vary between0.1 to 750 Torr. An oxygen source, for example, N₂ O or O₂, is excitedwithin the chamber 254 to produce a remote plasma. A silicon source, forexample, silane or disilane, is introduced into the chamber 218 eitherfrom chamber 254 or distributor 212. Ozone is introduced into chamber218 through distributor 212. The wafer is heated to, for example,between 200 to 500 degrees C. Ultraviolet light is generated with space220 as discussed above to provide the excitation discussed above. Afterthe deposition is performed, the gas and the heat is turned off and thechamber 218 can be again purged, if desired. After the wafer is removed,the chamber can be cleaned utilizing a remote plasma formed from, forexample, CF₄ and O₂. The pressure can be, for example, 0.1 to 750 Torrand the ratio of SiH₄ to O₂ can be, for example, 1 to 5.

One class of embodiments disclosed herein provides a deglaze processwherein the activated products of a source gas flow which includes botha fluorine source gas species or, alternatively, anhydrous HF and also alarge percentage of oxygen are flowed across a wafer surface downstreamfrom a plasma discharge which is remote from the wafer surface. Thisembodiment has the advantages that a dry deglaze process which does notselectively erode silicon is provided. This embodiment has the furtheradvantage that a deglaze process is readily combined sequentially with afollowing process step. For example, an in situ deglaze can be used toremove native oxides, and assure a clean interface for succeedingdeposition steps. The process module 570 shown in FIG. 9 can be usedwithout actuating the ultraviolet light or in the alternative anotherprocess module could be constructed without the space 220, ring 576, andthe other components associated with the production of ultraviolet lightin space 220.

A deglaze process has been successfully demonstrated as follows: Processgas flows of 300 sccm of He plus 2000 sccm of O₂ plus 250 sccm of CF₄were passed through a 400 W discharge, and were found to give aselectivity of 3:1 oxide to polysilicon measured using a thermal oxideas compared with polysilicon on oxide (on silicon). The oxide etch ratewas only 7 Å/min at room temperature, but this rate can readily beincreased by using higher temperatures.

Thus, the teaching of the present application in this respect is that avery high oxygen fraction can advantageously be used to perform deglaze,using a gas flow which has passed through a remote discharge. Theintroduction of this high fraction of oxygen serves to enhanceselectivity by lowering the etch rate of polysilicon. These gas flowswould not work as well without the remote plasma, since the additionalplasma bombardment would not permit as high a selectivity.

The sample recipes given can be modified in various ways in accordancewith the teachings of the present application. For example, to obtainhigher (oxide:silicon) selectivity, a higher fraction of O₂ can be used.Somewhat higher rates can be obtained by using higher flows of CF₄.Higher temperatures will also increase the rates. The 2.5 Torr totalpressure can be widely varied.

An attractive alternative embodiment is to use a reactor like that shownin FIG. 23, with process gas flows of (e.g.) 3000 sccm of He plus 3000sccm of O₂ plus 150 sccm of CF₄, at a total pressure of (e.g.) 2.5 Torr,with (e.g.) 400 Watts of RF power applied to the gas flows to generateactivated species, at a substrate temperature of (e.g.) 250 C.

FIG. 10 shows an overview of the physical configuration of a samplesystem using a single process module 204 like that of FIG. 9. Theoperation of the load lock lid 20 and the process module 204 includingthe wafer transport mechanisms and the isolation gate 31 (FIG. 4) whichseparates the vacuum load lock chamber 12 from the process module areall controlled by a computer control system 206 which can be, forexample, an 8088-based PC (e.g., a Texas Instruments ProfessionalComputer). The computer control system 206 provides control logic forall of the processes performed at the process station. Process menus canbe developed at the keyboard, stored in memory, and carried outautomatically by this computer control system 206. For example,therefore, the the number of particles, if any, below which the computercontrol system allows opening of the vacuum wafer carrier 10 can beprogrammed.

FIG. 11 shows a flow chart for the operation of such a computer controlsystem. The logic starts in step 800 and proceeds to enter steps 802 and804. After the vacuum wafer carrier 10 has been loaded and the load locklid 20 is detected to be closed in step 800, the roughing pump isolationvalve 702 is opened in step 804. The nitrogen isolation Valve 703 isopened in step 802 to supply nitrogen into chamber 12 (FIG. 1) toprovide a gas purge of the chamber 12 through manifold 22 (FIG. 1) asdiscussed above.

The logic then proceeds from steps 802 and 804. which do not need to beperformed simultaneously, to state 806 and step 808. In step 808 thecomputer control system 206 will monitor the pressure and throttle thegate or isolation valve 39 to provide the appropriate control. The loadlock is pumped down to a moderate vacuum. This is still a higherpressure than the pressure inside the wafer carrier, so that the vacuumwafer carrier door 14 will not open yet. In state 806, the pressure isheld at a moderate level until the load lock particle counter 850 whichincludes the particulate sensor 202 indicates that the level ofparticulates is acceptably low. If the count detected by counter is notthe appropriate count then the logic loops back to state 806. When theappropriate count is detected, for example, zero, then the logic exitsthe loop and enter state 810. In state 810, if no particulate isdetected for a predetermined period of time, for example, 60 seconds,opening (or closing of the vacuum wafer carrier 10 can safely bepermitted). Thus, if for some reason an unusually high concentration ofparticulates is introduced when a vacuum wafer carrier 10 is loaded intothe load lock, the system will not expose the wafers 48 to contaminationuntil the danger of particulate contamination has passed under the closeloop control system described above.

After the particulate sensors 202 and 208 (FIG. 9) have detected noparticulates for the predetermined period of time, the logic exits state810 and proceeds to steps 812 and 814. The isolation valve 702 is fullyopened in step 812. In step 814, the isolation valve 703 from thenitrogen supply is closed. The logic then proceeds to step 816. Whilethe logic is in step 816 the isolation valve 707 is opened and thepressure within chamber 12 is further reduced. The logic exits step 816and enters into state 818. The pressure within the chamber 12 ismonitored in state 818 and if the pressure has not reached the desiredlevel the logic enters step 820. In step 820, the throttle of isolationvalve 707 is adjusted and the logic re-enters state 818. When thepressure, has reached the desired level, the logic exits state 818 andenters step 822. In step 822, door 14 is opened.

Another branch in the control logic may be added to go through anotherpurge cycle if the particulate level has stayed at an unusually highlevel after a given period of time. Thus, without degrading throughput,this closed loop particle control system advantageously ensures that therisk of particulate introduction during periods of high ambientparticulate levels is minimized. This closed loop particle controlsystem also advantageously protects against accidental contaminationwhich could be caused by error in the sequencing of operations in amanually controlled system.

Further, the computer control system 206 allows the pumping system topump down to working pressure and control the level of particles presentwhen the door 14 (FIG. 1) is opened. The door 14 of the vacuum wafercarrier 10 is opened by rotating shaft 24 as discussed above. Such insitu particle counters, for example, counter 850 in FIG. 31, can bebuilt using a resonant circuit to measure charge transfer in ahigh-voltage vacuum-gap capacitor, or (for particles sufficiently large)by using a laser-driven optical cavity with a multiply-folded opticalpath, or by other means.

The isolation gate 31 (FIG. 3) can now be opened to permit passage ofarm 28 with the wafer 48 into the process module. This double inhibitionlogic is useful because neither the vacuum wafer carrier door 14 nor theisolation gate 31 into the process module can be opened until theparticulate level in the vacuum load lock chamber 12 has been measuredat an acceptably low level. These are separate techniques, and eithercan be used independently, although synergistic advantages can result ifboth are used together. The wafer 48 can then be removed from the vacuumwafer carrier 10 by the wafer transfer arm 28. The computer controlsystem 206 (FIG. 10) controls the transfer arm 28 to remove or replaceeach wafer 48 in any random order which may be programmed. The wafer 48is transferred with the side which will eventually contain activecircuit components facing down.

Optionally, other particle counters (or particulate sensors which betteradapted to sensing particulates at higher pressures) can be used tocontrol the nitrogen shower prior to initial pumpdown. That is, insteadof doing the nitrogen shower simply for a fixed duration, it may beprotracted if the particulate monitor shows that the box was in anunusually dirty environment. It may even be desirable to pump the loadlock down to a soft vacuum (using the roughing pump) and then bleed gasthrough the nitrogen shower ports, to create a downward flow. It mayalso be desirable to cycle the load lock from a soft vacuum (e.g. 100milliTorr or so) up to atmospheric again, by initiating another nitrogenshower cycle, if the particulate monitor indicates that that particulatelevel is still excessive at the time the load lock has reached a givensoft vacuum pressure.

The particulate sensor 208 as shown in FIG. 9 is connected to theinterior of the process module, and this is used to control anotherinhibit logic. A large fraction of the particulates which occurs in avacuum processing system is generated by the actual processes beingperformed. As an modification, to reduce particulate contamination fromthese sources, the isolation gate 31 (FIG. 3) to the process module, forexample process module 570 (FIG. 9) is not opened after a wafer 48 hasbeen processed until the particulate sensor 208 indicates an acceptablylow level of particulates inside the module. Again, this is anotherfeature which can be applied separately from the others just discussed,although synergistic advantages do result if the two are used together.

FIG. 12 shows a detailed view of one modification to a process module,such as the process module 570 shown in FIG. 9, which provides acapability for ultraviolet enhancement of process chemistries. Thecapabilities of this embodiment can be embodied in more conventionalreactor configurations as well, but they will be described in connectionwith a process module of this type because the features describedprovide particular advantages in this context.

FIG. 12 shows one embodiment for an ultraviolet enhanced vacuum processmodule 590. A process gas distributor 212 is supplied by the processpiping 216 and generates a downward flow of process gases throughopenings in the bottom of its ring in the top chamber 218. Thedistributor 212 provides a downward flow of process gases to the topchamber 218 near the wafer face 54 of wafer 48 which is facing downwardabove distributor 212 and supported by three support fingers 214 (onlyone of which is shown). The support fingers 214 are similar to pins 53in FIG. 3. These three support fingers 214 are usefully made of quartzor other high-purity dielectric material.

The process gas distributor 212 is a ring, of perhaps one half thediameter of the wafer 48 being processed, with hollow supports whichlead to the process piping 216. It is situated several, e.g. four,centimeters from the wafer 48. The exact dimensions of the process gasdistributor 212 are not critical. These parameters may be changed ifdesired, but if modified, they should be selected so that a fairlyuniform concentration of process gases and process gas products occursover the entire wafer face 54. For example, the spacing of the processgas distributor 212 away from the wafer 48 could be anywhere in therange from 1 to 15 centimeters. The process gases provided through theprocess gas distributor 212 may be of several different types, includingmixtures which include active species generated by a remote plasma.

The reaction of these process gases with the thin film materials on thewafer face 54 is enhanced by the ultraviolet light emitted by the inultraviolet plasma space 220 located below top chamber 218. A secondflow of process gases is provided from orifices 222 supplied by thepiping 230 into the ultraviolet plasma space or lower chamber 220,wherein a plasma is generated by RF power applied to front electrode224. The gas supplied can be, for example, H₂, Ar, or He. The frontelectrode 224 is perforated to permit passage of ultraviolet light, butalternatively it may be made with a composition and thickness to betransparent to ultraviolet. Ground electrodes for this plasma areprovided by structural metal elements and by the metal walls 228 of theprocess module. The frequency of the power applied to the electrodes toproduce the ultraviolet light can be, for example, 100 KHz or 13.56 MHz.Quartz baffle 232 which in this embodiment is approximately H-shaped incross section, and has an approximately cylindrical outer surface,separates the gas flows in the ultraviolet plasma space 220 from thosein the top chamber 218. Thus, the two chambers 218 and 220 not only haveseparate gas flows, with top chamber 218 being exhausted throughopenings 234 between the top of baffle 232 and wafer 48, and theultraviolet plasma space 220 being exhausted through openings 236between the bottom of baffle 232 and quartz plate 592. Chamber 218 andspace 220 may optionally even be operated at different pressures as longas the pressure differential does not lead to back-flow in the exhaustspace.

After the wafer has been positioned on the three support fingers 214 andthe module has been closed, power can be applied to the front electrode224 to generate a plasma, and a gas appropriate for the generation of aultraviolet plasma is admitted to the ultraviolet plasma space 220through piping 230. Appropriate gases include N₂, H₂, O₂, and many otherspecies. The particular gas can be chosen to match the ultravioletspectrum desired in a particular application. The ultraviolet-sourceplasma can be generated by using an appropriate gas or mixtures ofappropriate gases and appropriate pressures with greater than a minimumpower for the particular chamber configuration and structure, forexample, 50 watts.

In the embodiment shown in FIG. 12, the back side of the wafer 48 is inproximity to a transparent vacuum wall 238, and is supported with aslight spacing away from the vacuum wall. These features relateparticularly to embodiments with Rapid Thermal Processing (RTP)capability, which will be discussed in greater detail below.

In the embodiment shown in FIG. 12, the quartz baffle 232 includes amember 239, which is shown horizontal and substantially transparent toultraviolet. Member 239 forms the crossbar in the H shaped cross-sectionof baffle 232. This ultraviolet transparent window can be fabricatedfrom quartz or sapphire or other similar material.

Optionally, if complete separation of the gas flows is not necessary,and especially if very short wavelength operation is desired, the member239 can be made perforated rather than solid, or can be omittedentirely. This is shown in FIG. 13. The process module 600 is similar toprocess module 590 of FIG. 12. The gas distributor 602 is similar todistributor 212 of FIG. 12. The quartz baffle 604 is a cylindrical shape(shown as two rectangles in FIG. 13). The process gas to the top chamber605 is through gas distributor 602 and the ultraviolet plasma space 607is through piping 609. The front electrode 612 is similar to frontelectrode 224 in FIG. 12. However, now the process gas in the space 605can mingle with the process gas in the chamber 605 because the crossbarin the quartz baffle 232 (FIG. 12) is not present in quartz baffle 604.

FIG. 14 shows a process module 620 somewhat similar to process modules590 (FIG. 12) and 600 (FIG. 13). In FIG. 14, the plasma in theultraviolet plasma space 220 is driven by two electrodes 244 and 246which are shaped approximately as concentric cylinders. In addition, gasdistributor 248 in the ultraviolet plasma space 220 is different fromthe piping 230 in FIG. 12. The quartz baffle 232 in FIG. 14 is H-spaced.Also process module 620 includes a third gas feed 250, which can be usedto provide species generated by a remote plasma, as will be discussedbelow. The gas feed 250 is in addition to gas distributor 212 which is aring in the top chamber 212 and feed 256 which provides gas intoultraviolet plasma space 220. Further, a susceptor 252, which is RFpowered in place of the transparent vacuum wall 238, so that a plasmacan be generated in proximity to the wafer face 54. The electrode 244forms a slip-fit with the feed 250. This slip-fit is not sealed butmerely vented downward.

In this application, when a plasma is referred to as being "inproximity" to a wafer, it is meant that the plasma is sufficiently closeto the wafer that the DC bias across the dark space at the edge of theplasma induces significant plasma bombardment of the wafer face. Thedegree of bombardment will be more or less in accordance with the amountof DC bias, which is controlled by pressure, power levels, and, to someextent gas flow composition.

Thus, FIG. 14 shows a separate feed path being provided for activatedspecies generated by a plasma which is remote from the wafer face 54. Inthis class of embodiments, a process module is configured so that anintegrated circuit wafer 48 can be exposed to activated speciesgenerated by a first plasma which is separate from the wafer but is inthe process gas flow stream upstream of the wafer 48, and also exposedto plasma bombardment generated by a second plasma which has a darkspace which substantially adjoins the surface of the wafer. The in situplasma is relatively low-power. so that the remote plasma can generateactivated species, and therefore the in situ plasma power level andfrequency can be adjusted to optimize the plasma bombardment energy.

In particular, the embodiments described derive special advantages fromthe combination of a remote plasma in the gas feed with a low-powerplasma in situ. The use of a remote plasma means that a high density ofactivated species can be provided at the wafer surface, and the use ofthe low-power plasma in situ means that sufficient plasma bombardmentcan be provided to cause anisotropic etching, while limiting the plasmabombardment energy and flux to only that necessary to induce the desireddegree of anisotropy. This advantageously permits the damage which canbe caused by excessive plasma bombardment energy can be readily avoided.This also advantageously permits the chemistry of the reaction to befine-tuned. It is desirable to have the plasma bombardment shift thesurface chemistry enough to provide anisotropy, but two other primaryconstraints on any plasma etching process are selectivity and control ofextraneous deposition, and the choice of a chemistry to optimize all ofthese conditions may be very constrained. The ability to independentlyoptimize bombardment conditions provides advantages in developingoptimized chemistries, as some of the specific examples discussed belowdemonstrate. Moreover, the ability to provide a high density ofactivated species under low-bombardment conditions means that processescan be performed at high throughput under low-bombardment conditions,which was not readily achievable prior to the process modules disclosedherein. Another advantage of using a low-power plasma for the in situplasma is that wafer heating (which degrades the selectivity to resist)can be minimized.

In a typical usage, the remote plasma will be operated at 300 W or more,and the in situ plasma will be operated at 100 W or less: however, itmay be advantages to operate at higher powers, for example, withAluminum doped with Copper films. Thus, it should be understood that theremote plasma can be operated at four times or more the total powerlevel applied to the in situ plasma. In other alternative versions, thein situ plasma may operated at power levels as low as 25 W. Theadvantage of reduced plasma bombardment energy is partially independentof the attainment of low power. Thus, the in situ plasma can be operatedat a DC bias of 250 V or less, for example, a typical level can bewithin the 25 to 1000 Volts range.

FIGS. 9 and 32 show an overview of a process module with thiscapability. In FIG. 9, the remote plasma chamber 254 is connected to theprocess module by a quartz outlet tube 256.

FIG. 15 shows a remote plasma chamber. A magnetron 264 which, e.g.,operates at 2.45 GHz, is directly coupled to a resonant cavity 260which, e.g., is made of anodized aluminum, and has dimensions of about1.5 by 3 by 9 inches. A gas input tube 266 is connected to one or moremass flow controllers, to provide a desired flow of process gases, andleads into a gas passage 270 which runs through the resonant cavity 260and leads into the quartz outlet tube 256. It then passes through ashielded volume which protects against RF leakage out of the cavity.Since the quartz used has an outer diameter of less than aquarter-wavelength, e.g., about 1 inch in this example, which is ashield 268 of the order of one wavelength (or more) long will providereasonable isolation. The shield 268 extends around the quartz outlettube 256 and usefully around the whole length of the outlet tube 256, upto the point where it enters the reactor module. A tuning stub 272permits tuning the cavity to resonance. A nitrogen purge is preferablysupplied to the interior of the resonant cavity 260, to prevent ozonegeneration. Cooling lines (not shown) can also be useful. The outlettube would be connected to, for example, the gas feed 250 (FIG. 9).

In this embodiment, the gas flow through the gas passage 270 provides asignificant fraction of the total loading of the resonant microwavesystem cavity plus magnetron. Thus, it is useful not to turn on thepower until gas flows and pressures have been established. In a processwhere, for example, 400 W of power will be applied, the pressure shouldbe at least 500 mTorr, and the flow rates at least 500 sccm, before themagnetron 264 is powered. These are conservative numbers, but they doserve to prevent arcing in the cavity or magnetron. At higher powers, ofcourse, higher minima would be used. For example, in sample processeswhere 5000 sccm of total gas flow is used, powers of as much as 1000 Wcan optionally be used.

Note that the power efficiency of the remote plasma will be affected bythe volumetric ratio of the gas passage 270 to the interior of theresonant cavity 260. Thus, the gas flow passage 270 could be made,instead of the roughly cylindrical shape shown, be modified to have ashape which filled up more of the volume of the cavity.

Instead of the magnetron 264 directly abutting the resonant cavity 260,of course, a waveguide or other RF transmission structure could be usedto connect them, according to the normal principles of microwaveengineering. Thus, it may alternatively be advantageous to locate theresonant cavity 260 physically inside the process module, to minimizethe transit time during which the activated species can relax,recombine, or decay before they reach the wafer face.

In an alternative embodiment, a conventional microwave component knownas a three-port circulator can be used to couple both a transmitter anda receiver to the same antenna without coupling the transmitter to thereceiver. It could be used to partially de-couple the magnetron 264 fromthe resonant cavity 260, so that, under conditions where a largereflected power was returned from the cavity, a separate resistive loadwould assume some of the loading function.

This has the advantage that the sensitivity of the RF system to loadingvariations caused by changing process conditions is greatly reduced.This has the further advantage that one RF power source can be coupledto more than one remote plasma generation cavity, if desired.

In the embodiment shown in FIG. 9, the quartz outlet tube 256 isconnected to the third gas feed 250, like that shown in FIG. 14, by anon-contact slip fit joint 258. This loose slip fit will permit some ofthe gas feed to leak out directly into the exhaust space duringprocessing, but this is only a minor problem. The advantage of using aslip fit here is that it accommodates the vertical motion of the processchamber while still permitting essentially the whole path of the gasflow from the remote plasma chamber 254 to be conducted through quartztubing. As discussed above, the vertical motion serves to open and closethe process chamber for wafer insertion and removal. This has been foundto be a useful feature in practice since many of the activated speciesgenerated by the remote plasma will be very active. These active speciesinclude radicals such as O, quasi-stable molecular species such asoxy-halogen compounds, molecules in quasi-stable states with highelectron energies, and, especially close to the plasma, a significantfraction of ionized species. The tube used to carry this flow should beboth as inert as possible in order to resist attack and be as pure aspossible to minimize contamination of the wafer by species which may beremoved from the tube walls by the flow of the activated species. Quartzmeets both of these criteria for most sources. If the gas flows to beused include fluorine sources the tubing can be made of sapphire, orsintered alumina, or copper. Additionally, depending on the processchemistries used, it may be simpler to use quartz if the erosion of thequartz outlet tube 256 and the modification of the chemistry in the gasflow can be tolerated in the particular process being run. FIG. 16 showsdetails of another process module 630 which in many respects is similarto that shown in FIG. 14. A wafer 48 is held against a conductivesusceptor 300 which may be of aluminum, or optionally of silicon if itis useful to modify the process chemistry (e.g. to create afluorine-deficient plasma near the wafer face 54. The susceptor 300 islocated above the wafer 48 with the top chamber 218 located below thewafer 48. The susceptor 300 is cooled by passages 302. If desiredsusceptor 300 can be heated through passages 302 or by utilizing heaterrods (not shown) passing through susceptor 300. The wafer 48 is heldagainst susceptor 300 by the three support fingers 214 in FIG. 16 withits face 54 facing downward away from susceptor 300.

A process which can be performed in the process modules with ultravioletlight generation and remote plasma capability as disclosed herein, forexample, 630, is the deposition of conductive films. Conductive filmscan be produced by reducing or decomposing metal organic compounds withremote microwave activated species. For example, Zn, Al, In or Pb filmscan be produced by reacting metal organic compounds such asdimethylzinc, trimethylaluminum, trimethylindium or tetramethyllead,respectively, with radicals such as hydrogen or argon. In a sampleembodiment, a silicon or HgCdTe substrate (wafer) is transferred intothe process chamber. The chamber is evacuated to a pressure of less than10⁻⁶ Torr. The chamber is then purged with an appropriate gas, forexample, hydrogen, which passes into the process chamber through themicrowave cavity at, for example, 100 sccm, if desired. The chamber isthen brought to a pressure of 0.3 Torr. The substrate is heated to 50degrees C. Dimethylzinc is introduced into the chamber throughdistributor 212 at, for example, 6.6 sccm. Active hydrogen radicals arethen generated in the remote microwave cavity at, for example, 6 watts,and are introduced into the chamber through feed 250 to mix thedimethylzinc to produce metallic zinc which deposits onto the substrateand methane, which is pumped from the process chamber. Zn films areproduced at 60 Angstroms/minute with 25×10⁻⁶ Ohm-cm electricalresistivity.

A process which can be used with the process module 630 as well as theother process modules with in situ ultraviolet energy generationcapability is to grow native oxides on HgCdTe. After the wafer isdisposed in process chamber 218 and the chamber is closed, the chamberis evacuated to a desired low pressure, for example, 0.05 Torr. A purgeof the chamber can be performed if desired using an appropriate gas, forexample, O₂ or an inert gas. A remote plasma generated from a source ofoxygen, for example, O₂ or N₂ O, is introduced into chamber 218 toperform a cleanup if desired. The remote plasma is shut off. The chamberis evacuated and purged with O₂ or an inert gas, if desired. Ultravioletlight is generated within space 220 and coupled into chamber 218. Theultraviolet light provides the required excitation of the gases withinchamber 218. The ultraviolet light is maintained for an appropriateperiod of time, for example, 1 hour. The chamber is then evacuated andpurged with an appropriate gas, for example, N₂. The chamber is thenopened and the wafer 48 removed.

Another process which can be utilized with the process modules disclosedherein with ultraviolet light and remote plasma capability, for example,module 630. The wafer is transferred into the process chamber and thechamber closed. A purge with an appropriate gas, for example, N₂ can beperformed. A remote plasma is generated from N₂ O and introduced intochamber 218 through feed 250. A silane gas, for example, SiH₄ isintroduced into the chamber through distributor 212. Ultraviolet lightis produced within space 220 and coupled into chamber 218. It will beabsorbed in part by the N₂ O gas in chamber 218. After the deposition iscompleted, a cleanup operation can be performed, if desired, byutilizing a remote plasma generated from SF₆.

A process gas distributor 212 provides process gases to the top chamber218 near the wafer face 54. Another process gas distributor 306 providesgases to the ultraviolet plasma space 220 wherein a second plasma,remote from the wafer face 54, is optionally generated by applying RFpower to front electrode 224. The species flowed through distributor306, and the power level applied to front electrode 224, are chosen toilluminate the wafer face with the desired wavelength and intensity ofultraviolet light. The quartz baffle 232 directs the gas flow out of topchamber 218 and ultraviolet plasma space 220 so that the gas flowthrough the ultraviolet plasma space 220 does not contaminate topchamber 218, which is a similar gas flow to that shown in FIG. 12. Thethird gas feed 250 provides a gas flow which has been activated by aremote plasma chamber to top chamber 218 near the wafer 48. Voltage forthe in situ plasma is applied to susceptor 300.

A process will now be described wherein a compound, such as zincsulfide, is deposited from a gas phase in a reactor which is compatiblewith a vacuum processing system which includes vacuum wafer transport.Two gas distributors are used, each connected to a supply of one or morereagent gases, to improve uniformity and/or avoid gas phase nucleation.This process embodiment has the advantage that II-VI films, such as ZnS,can be rapidly deposited with good uniformity and good film quality.

The deposition of sulfide, selenide, and telluride films such as CdS,ZnS, PbS, CdSe, ZnSe, and other II-IV combinations can be produced byutilizing metal organic compounds and sulfide or selenide gases. Theorganometallic compounds (metal organic) can be, for example, from thegroup of dimethyltellurium, dimethylzinc, trimethyaluminium,tetraethylead. The sulfide can be, for example, hydrogen sulfide and theselenide gas can be, for example, hydrogen selenide. The requiredexcitation can be provide by either or both a inert gas actuated remoteplasma chamber 254 introduced into the process chamber or ultravioletlight generated in space 220 which is coupled into the process chamber.The susceptor 300 can be heated by utilizing heater rods (not shown)passing through the susceptor. It is also possible to dope the depositedfilm such as ZnS doped with PbS. For example, a mixture of tetraethyleadand dimethylzinc is introduced into the chamber through one distributor310 and hydrogen suflide is introduced through a second distributor 312to produce a mixture of ZnS and PbS.

In a sample embodiment, a HgCdTe substrate was used with a very thinpassivating dielectric layer already present (in this case, a thin filmof sulfides, less than 100 Ångstroms thick). H₂ S was flowed at 30 sccmthrough one gas distributor, and dimethylzinc ((CH₃)₂ Zn) was flowed attwo to three sccm through the other distributor, at a substratetemperature of 50 degrees C. and at a total pressure of 150-200milliTorr. These conditions resulted in growth of a film of goodelectrical quality at a rate of about 350 Angstroms per minute.

Optionally, the passivating layer can also be formed in the same reactorjust before the ZnS deposition is performed. This is especiallyadvantageous for the fabrication of MIS gates on HgCdTe. In a sampleembodiment, a HgCdTe substrate has its native oxide removed with diluteHCl, rinsed with DI (deionized) water, dried with nitrogen andtransferred to the process chamber under vacuum. The chamber is purgedwith hydrogen sulfide at, for example, 30 sccm and the chamber isbrought to a pressure of 0.2 Torr and the substrate to a temperature of100 degrees C. The hydrogen sulfide and HgCdTe surface is illuminated byan additional source of ultraviolet light to produce hydrogen-bearingand sulfur-bearing excited state species (atoms and radicals) whichchemically reduce residual oxides on the HgCdTe and create a thin,passivating sulfide film. ZnS is then deposited over the passivatedHgCdTe by introduction of dimethylzinc at, for example, 2 to 3 sccm.

The ZnS growth rate was found to be very sensitive to temperature, and ahigher substrate temperature is probably desirable. While the stabilityof the HgCdTe material sets the maximum growth temperature at about 120degrees C. or less, it is believed to be desirable to increase thegrowth temperature to the range from 90 degrees to 120 degrees, toachieve rapid growth of a high quality film. While gas phase reaction ofthese gases is not a large problem at 50 degrees C., it becomes muchmore significant at temperatures of 100-120 degrees C. Another advantageof the process module 640 configured to be used as a reactor is tofacilitate the use of these higher temperatures without incurringproblems due to reaction in the gas phase.

To achieve a smoothe film, a diluent gas can be mixed in with thereagent gas flow, and/or the reagent gases can be flowed at higherrates. Suitable diluent gases would include hydrogen, helium, and argon.

Growth of a zinc sulfide film under illumination from an in situultraviolet source has also been tested, and it has been found that theultraviolet irradiation provides substantially faster film growth. Theadditional ultraviolet radiation could be useful in other depositions.

FIG. 17 shows the process module 640 which is used as a reactor. Thereactor configuration is useful for the deposition process describedabove as well as other types of deposition. Distributors 310 and 312each separately release a flow of a process gas inside a baffle 314,which directs the flow of gases upward to the top chamber 218 near theface 54 of wafer 48 which is held against a conductive susceptor 300 bythe three support fingers 214 (only one is shown in FIG. 17 but allthree are shown in FIG. 3).

Note that, in the embodiment shown, the three support fingers 214 arerelatively long, and are supported at their bases, well away from thetop chamber 218, by respective flexures 316. Each finger is supported bytwo (or more) leaf springs (not shown), so that the finger can bedeflected vertically, but will always tend to maintain a vertical axis.The advantage of this arrangement is that it helps in providing areactor wherein nearly every exposed surface which is near the wafersurface 54 and, specifically. every surface which is upstream from thewafer surface is made of quartz or, alternatively, another comparablypure and inert material. The species (CH₃)₂ Zn is quite reactive, andminimizing exposed surfaces other than quartz assists in avoidingdeposition (which can lead to particulate contamination). Moreover, inthis embodiment a mating pair of Teflon-coated (TM) baffles 318, 320 isused to separate the exhaust gas flow from the bellows 124, to avoiddeposition on the bellows which might flake off when the bellows move.

Several of the embodiments described in the present application use aradiant heat source to permit rapid heating of a wafer, and provide theadvantages of high-temperature processing without the long thermalramping times normally required. FIG. 18 shows an arrangement forperforming rapid thermal processing.

FIG. 18 shows a process module 650 wherein a wafer 48 is held against orin close proximity to a transparent vacuum wall 238. As shown in FIG.18, a ring of heating elements, for example 18 1-kW high-temperatureincandescent lamps 330, is mounted in an upper fixed reflector 334 (FIG.19A). The upper fixed reflector and a lower fixed reflector 332 helpmaximize the heating efficiency, i.e. improve the fraction of opticalpower emitted by the high-temperature incandescent lamps 330 which isoptically coupled through the transparent vacuum wall 238 to wafer 48.The control system 206 can use temperature sensors to control alteringthe shape of the reflector by moving reflector 336 up and down toselected positions.

FIG. 19A shows the geometry of the upper fixed reflector 334 incross-section. The surface of reflector 334 has three straight lines inproximity to the lamp, i.e. surfaces 338, 340 and 342 with each surfaceshaped roughly as conic frustum and positioned to reflect light directlyfrom the high-temperature incandescent lamps 330 through the wall 238.The geometric optics of this light path, in this embodiment are shown inFIG. 19A.

It must be appreciated, however, that, while the specific embodimentshown has demonstrated good results and advantages, a wide variety ofother reflector geometries could be substituted for that shown, whilestill retaining the advantages of the concepts described herein. Thearrangement of the heating elements and the reflectors forms a heatingmodule. Other types of heating modules are possible with the heatgenerated being thermally communicated to the wafer 48 with thearrangement of FIG. 18 being one example.

A movable upper reflector 336 (FIG. 18) is controllably movablevertically by drive 344. The reflector 336 is located within a circularopening in the center of upper fixed reflector 334. The movement ofreflector 336 permits the area distribution of one component of theradiant heating pattern to be controlled, as shown in FIGS. 19B and 19C,to result in heat flow distributions as shown in FIG. 20. The drive 334is located above the reflector 336 as shown in FIG. 18.

As shown in FIG. 20, the upper curve 652 shows the distribution of theheat energy from the edge of the wafer 48 in FIGS. 19A, 19B, and 19C (atthe left as in FIG. 20) to the center of the wafer 48 (at the right inFIG. 20). The area between the dotted line 654 and solid line 656 is thecontribution of the reflector 336 with the area below the solid line 656being the contribution of the fixed reflectors 332 and 334. Thisrepresents the relative distribution of the thermal energy when thereflector 336 is in the up position as shown in FIG. 19C. The curve 659of FIG. 20 shows the relative distribution of the thermal energy whenthe reflector 336 is in the down position as shown in FIG. 19B. The areaunder solid line 657 of curve 659 shows the contribution of the fixedreflectors and the area between solid line 657 and dotted line 658 isthe contribution of reflector 336.

When the movable upper reflector 336 (which has a shape at its tipsomewhat similar to a cone with a 90 degree tip angle) is in its lowerposition, as in FIG. 19B, additional heating is provided to the edge ofthe wafer: but when the movable upper reflector 336 is in its upposition, as in FIG. 19C, this component of radiation will not bepreferentially coupled to the edge of the wafer, so that the center ofthe wafer receives additional heating. For clarity, FIGS. 19B and 19Ctrace only the component of optical radiation which is emitted parallelto the lamp filament; but it may be seen, in FIG. 19B, that lightemitted over a significant range of angles will be similarly deflected.

Reflectors 332 and 336 are, for example, made of aluminum coated withgold, and can be cooled by water flowing in passages within thereflectors. Reflector 334 could be coated with any suitable reflectivematerial as desired.

The power input to these high-temperature incandescent lamps 330 iscontrolled by one of the control signals provided by the computercontrol system 206 (FIG. 31). Generally, power on the lamps is ramped ata high rate to a high power level (e.g. 40% of full power) and heldthere for some period of time depending on the process (e.g. 15seconds). Power is then ramped back to a lower steady state level untilthe process is complete (e.g. to 16% of full power).

As another example, if the particular process being run requires thewafer to be held at a temperature of 600 C. during processing, the lamppower would be turned on at (for example) 30% of full power (i.e. at5400 Watts total), and held at that level until the wafer reachesapproximately the desired processing temperature, at which time thepower is ramped back down to a level which will maintain the wafer atthe desired processing temperature until the process is complete.

In a sample system where 18 1000 Watt incandescent lamps are position ina ring in a reflector (made of gold-plated aluminum) with a 6 inchdiameter which faces a 6 inch quartz plate. The exposed portion of thequartz plate provides the transparent vacuum wall 238 and has an openingjust large enough to permit radiant heating of the backside of a 4 inchwafer which is held close to the wall 238.

In a sample process embodiment, with the lamp powers just given, thewafer is held at 600 C. while process gas flows of 40 sccm H₂ plus 8sccm of WF₆ are applied to its front side at a total pressure of 500milliTorr. This chemistry has successfully demonstrated high-qualityconformal deposition of thin films of tungsten at 2000 Å per minute.

In one embodiment, a combination of stationary reflectors, and lamps areused to heat the wafers rapidly to approximately 900° C. The wafersheated to approximately 1100° C. at at least 200° C. per second withoutany slip being introduced into the crystalline structure. The heatingdevice is a dynamic radiant heat source, described in further detailbelow.

Both the intensity and the radial distribution of the incident radiantenergy 22 can be adjusted. The adjustment of the power input to thelamps can be used to adjust the temperature of the wafer. Thisembodiment utilizes a temperature measuring device (such as an opticalpermitter) to detect the temperature changes in the wafer beingprocessed. In order to achieve the appropriate radiant energydistributions across the wafer during heat-up and cool-down, the movablereflector 336 need only be moved a total distance of approximately 11/2inches. For example, curve 652 represents the distribution duringheat-up and curve 659 represents the distribution during cool-down.

The embodiment shown in FIG. 18 has successfully demonstrated controlsuch that temperature variations across the radius of the wafer wereheld to less than 1% during ramping of the temperature of the wafer at arate of, for example, 200° C. per second, to a final temperature of1100° or greater.

After the desired processing operation has finished, the gas suppliesare cut off or optionally switched over to inert species, and a holdingtime may be optionally interposed for a controlled cool down of thepartially fabricated integrated circuit wafer, or for the settling ofpossible suspended particulates, before the process chamber is opened. Agas purge could also be performed if desirable.

FIGS. 21A and 21B depict two modifications which reduce conductivethermal coupling between the wafer 48 and a transparent vacuum wall 238in a vacuum processing system with rapid thermal processing capability.Note that the reflector configuration shown in these Figures is shapeddifferently than that shown in FIG. 18.

FIG. 21A shows an example of an embodiment wherein most of the surfacearea of the wafer 48 does not make contact with the transparent vacuumwall 238. Instead, the transparent vacuum wall 238 is formed to includea downwardly extending ring 350 which makes contact with wafer 48 closeto the circumference 49 of the wafer 48 when the wafer 48 is raised bythe three support fingers 214. A purge gas line 352 permits a purge gas(e.g. Ar, Argon) to be supplied to the backside of the wafer 48.

FIG. 21B shows an example of an embodiment wherein the wafer 48 does notmake direct contact with the transparent vacuum wall 238 at all.Instead, a second transparent plate 358, which is thinner than thevacuum wall 238, contacts the wafer 48 when the it is pushed against itby fingers 214. The plate 358 is located below wall 238. Since thesecond transparent plate 358 is substantially thinner than thetransparent vacuum wall 238, conductive coupling to it exerts lessthermal loading on the wafer than full contact with the transparentvacuum wall 238 would. In the sample embodiment, the vacuum wall is 0.5inches thick, and the second transparent plate 358 is 0.06 inches thick.Again, a purge gas line 352 permits a purge gas (e.g. Ar) to be suppliedto the backside of the wafer 48. It is useful to have the secondtransparent plate 358 is spaced away from the transparent vacuum wall238.

The purge gas supply used in both these embodiments helps in achieving auniform temperature distribution across the wafer. In addition, purgegas supply to areas near the transparent vacuum wall helps preventdeposition or etching effects from accumulating to degrade transparencyor generate particulates.

FIG. 21C shows yet another technique for reducing conductive thermalcoupling between wafer 48 and a transparent vacuum wall 238 in a vacuumprocessing system with rapid thermal processing capability. The wafer 48is supported by three support fingers 214 at a height such that, whenthe top chamber 218 is closed, the wafer is a small distance (e.g. 1 mm)away from the vacuum wall 238.

The techniques for reducing conductive thermal coupling shown in FIGS.21A, 21B, and 21C are useful for wafer processing they could be appliedto other types of work pieces.

Since the transparent vacuum wall 238, which can be made of quartz,experiences large temperature swings and must maintain a vacuum seal toa chamber which is generally fabricated out of metal, which has a quitedifferent coefficient of thermal expansion, it may be advantageous touse a specialized vacuum seal like that shown in FIG. 21D between thetransparent vacuum wall 238 and the reactor body. Such seals (which areknown commercially as Helicoflex (TM) seals) include an Inconel (TM)helix 660 enclosed in a stainless steel jacket 662, with a soft metaljacket 664 (e.g. aluminum) surrounding the sealing surface of stainlesssteel jacket 662. When the seal is tightened down, the plasticdeformation of the soft metal jacket 664 provides a leak free seal.Elastic deformation is primarily provided by the stiff Inconel helix660.

Such seals have been suggested for use in ultra high vacuum systems(which are periodically baked out, at temperatures of, e.g., 600 degreesF.) as indicated in: I. Sakai et al., "Sealing Concept of Elastic MetalGasket `Helicoflex`", 32 Vacuum 33 (1982); Hajime Ishimaru et al.,"Bakable Aluminum Vacuum Chamber and Bellows with an Aluminum Flange andAluminum Seal for Ultra High Vacuum", 26 IEEE Transactions on NuclearScience 4000 (1979): R. B. Fleming et al., "Development of Bakable Sealsfor Large Non- Circular Ports on the Tokamak Fusion Test Reactor", 17Journal of Vacuum Science and Technology 337 (1980); Hajime Ishimaru etal., "Bakable Aluminum Vacuum Chamber and Bellows with an AluminumFlange and Aluminum Seal for Ultra High Vacuum". 15 Journal of VacuumScience and Technology, 1853 (1978); all of which are herebyincorporated by reference. Applicants believe that such seals wereoriginally marketed for their ability to tolerate high pressuredifferentials at relatively high temperatures (e.g. 600 degrees F.) andstill maintain a vacuum seal, but it is not known that such a seal hasever been suggested to provide a vacuum seal between two dissimilarmaterials in rapidly changing temperature environment, nor specificallyfor rapid thermal processing in vacuum processing systems.

It should be noted, however, that applicants' experimental results haveshown that an elastomer seal will generally serve satisfactorily, aslong as the elastomer seal material is not exposed to the radiantheating.

As mentioned above, the radiant heating modules usefully include coolingpassages, since the power levels typically used (12-50 kW lamp power)are such as to promptly melt even a gold-coated aluminum reflector.However, FIG. 22 shows an alternative structure, wherein this isachieved indirectly. Part of the reflector 360 does not include coolingpassages, and therefore the overall width of this embodiment of theradiant heating module is less than it would otherwise be. Cooling isachieved by choosing a size for the sidewalls of reflector 360 such thatthe radiant heating module is a slip fit into the inside diameter ofhousing assembly 362, which includes cooling passages 364. Thus, whenthe lamp power is turned on, the reflector 360 will heat up and expanduntil its sidewalls make good contact to the housing assembly 362; butat that point thermal conduction into housing assembly 362 will provideefficient cooling, so that the heating of reflector 360 is inherentlyself-limiting. The base 366 of the radiant heating module has its owncooling passages (not shown), but these passages and their connectionsdo not increase the overall width of the heating module. Thus, theexample shown in FIG. 22 provided a heating module which fit into astandard 10-inch vacuum flange, while providing a radiant heat sourcealmost 10 inches wide. The depth of seating is of course chosen so thatefficient radiative coupling through transparent vacuum wall 238, behindwhich lies top chamber 218. The enhanced vacuum flange compatibilitymakes this embodiment particularly advantageous for use in combinationwith an ultra-high vacuum process station (i.e. a process module whichoperates at pressures of 10⁻⁹ Torr or less).

The process module shown in FIG. 22 has separate energy sources forinternal remote microwave plasma generation, RF in situ plasmageneration, and radiant heat applied to the same process chamber withinthe module. The energy sources can be separately controlled eithersingly or in any combination. The process module provides dry in situcleanup, high temperature native oxide removal, enhanced film depositionutilizing Radiant Heat. It is also capable of low temperature epitaxialfilm growth with a remote plasma source combined with radiant heat.Furthermore, it is capable of dry etch, including isotropic andanisotropic processes, by using in situ RF and remote plasma incombination. Pre-etch, etch, and post etch processes, direct reactand/or rapid thermal processes can also be performed. The process modulecan, therefore, sequentially perform several different process withoutmoving the wafer.

As shown in FIG. 23, a wafer 48 is shown below a transparent vacuum wall238 which is located above and spaced a short distance away. A purge gasline 352 is provided to supply gas to the face of wafer 48 which isclosest to wall 238. The arrangement of the wafer 48, wall 238, and theheating module is similar to that in FIGS. 21A and 21B. However, in FIG.23 a silicon electrode 670 is provided between wall 238 and wafer 48. Itis the silicon electrode which will be heated directly and the waferwill be heated by thermal conduction. The silicon electrode 670 isconnected around its edge to a RF conductor ring 672. Voltage for the insitu plasma close to the face 54 of wafer 48 is supplied to siliconelectrode 670 through RF condutor ring 672. The wafer 48, siliconelectrode 670, and RF conductor ring 672 are all electrically coupled.FIG. 23 shows a process module 675 which can have both remote (suppliedby a gas distributor such as feed 250 in FIG. 16) and in situ plasma(through a gas distributor such as distributor 212 in FIG. 16).

FIG. 23 has four separate energy sources, internally generatedultraviolet energy, remote MW (Microwave) plasma generation. RF in situplasma generation, and radiant heat. Each source is separatelycontrollable and can be used singly or in any combination. Processmodule 675 can provide dry in situ cleanup. Process module 675 can beused for high temperature native oxide removal, enhanced film depositionutilizing untraviolet light and radiant heat simultaneously, or anyother combination of energy sources desired, low temperature epitaxialfilm growth with remote MW (Microwave) plasma source combined withradiant heat, or any other combination of energy sources desired, dryetch, including isotropic and anisotropic processes, by using in situ RFand remote MW (Microwave) plasma in combination, or any othercombination of energy sources desired Pre-etch, etch, and post etchprocesses, and direct react and/or rapid thermal processes.

The process module 680 shown in FIG. 24 is similar to process module 675of FIG. 23 but with the inclusion of an additional source of ultravioletlight. The lamp module 682 is located is located above transparentvacuum wall 238. A wafer 48 is shown located below wall 238. A siliconelectrode 670 is located between wall 238 and wafer 48. The siliconelectrode 670 is spaced from wall 238 and in contact with wafer 48. A RFconductor ring 672 is in contact with the silicon electrode 670 tosupply RF power for the formation of in situ plasma adjacent face 54 ofwafer 48 in top chamber 212. Gas purge feed 352 performs the samefunction as described above. Remote plasma is provided through feed 250.Process gas distributor 212 provides process gas adjacent the face ofthe wafer 48. Quartz baffle 232 is H- shaped in cross-section. Fingers214 support the wafer 48 against electrode 670. Gas distributor 248supplies gas for ultraviolet plasma space 220. Electrodes 684 and 685provide arranged along the inner and outer vertical walls of space 220provide the necessary voltage for the formation of plasma within space220. In general, the lower portion of the module 680 is similar tomodule 620.

One process which has been successfully demonstrated permits etchingcopper-doped aluminum (Al:Cu) films, for example, heavily copper-dopedaluminum. RF power is used to generate a plasma and provide plasmabombardment at the wafer face, and the feed gas mixture includes BCl₃,chlorine, and a hydrocarbon source (e.g.. an alkyl, such as methane).Depending on the underlying material, a post-etch stage at lowerpressure may be used to remove low-volatility residues.

A sample embodiment of the process discussed has been successfullydemonstrated as follows: The starting structure included a 5000 Å thicklayer of aluminum doped with 2% copper. Initial gas flows included 60sccm of BCl₃, 20 sccm of Cl₂, and 5 sccm of CH₄, at a total pressure of100 milliTorr and an applied RF power level of 350 Watts, in a singlewafer reactor wherein the water is held in a face-down position. Ingeneral, the power supplied could be between 300 and 1000 watts. In anexample, of how the flow rates can vary. Cl₂ could have flow rates withthe range of 10 to 100 sccm. BCl₃ within the range of 60 to 250 sccm,and CH₄ between 0 to 15 sccm. The upper limit of the pressure is about0.5 Torr.

In a first embodiment, it was found that these conditions would provideclean removal of Al:Cu over oxide. In a second embodiment, it was foundthat, when a copper-doped aluminum film over tungsten was etched withthese conditions, some copper residue would remain. In this secondembodiment, a post-etch was used, in which, for 120 seconds, the gasflows were changed to 90 sccm of BCl₃ and 15 sccm of Cl₂ at a totalpressure of 40 milliTorr and an applied RF power level of 250 Watts. Theresulting structure showed nearly vertical etched sidewalls, little orno line width erosion, and approximately 2.5 to 1 selectivity tophotoresist, and left a clean surface (without any copper residues).

While this embodiment provides tremendous advantages, however, anotherembodiment provides yet further advantages. The reactor used is one likethat shown in FIG. 23 and 24, which permits both radiant heating andplasma bombardment to be applied to the wafer face. During the etch, thewafer is heated to (e.g.) about 200 C, which prevents copper residuesfrom remaining in place.

A further advantageous use of the radiant heating capability in thisembodiment is to enhance removal of residues from the chamber walls. Forexample, a very efficient chamber cleanup can be performed, after thewafer has been removed, by heating the susceptor to a significantlyhigher temperature than the processing temperature (e.g. 700 C.). Sincethe processing chamber is so small, the chamber walls will all be atleast somewhat thermally coupled to the susceptor by radiant heattransfer. A feed gas which will produce very active dissociationproducts in a plasma can be flowed in, and the combination of the hightemperature and the active species will remove residues very fast.Suitable feed gases would include a chlorine source such as BCl₃, or afluorine source such as SF₆.

In an alternative embodiment, radiant heating is used to heat the waferto temperatures of, e.g., several hundred degrees during the process.This process can provide rapid etching of heavily copper-doped aluminum(e.g. 2% copper) without leaving copper residues on the wafer. Oxygenwould also have to be utilized in the cleanup operation.

FIG. 25A shows an overview of a module for edge-preferential processingfor photoresist edge bead removal and for simultaneous photoresist bake,but the concepts described here are also applicable to systems foraccomplishing other process steps. FIG. 25A shows a process module 690which is connected, in this embodiment, by a quartz outlet tube 256 to aremote plasma chamber 254 which generates activated species in theprocess gas flow, as discussed above. A conical baffle 400 is used toprovide enhanced reaction rates at the edge of the wafer. The baffle 400and the support 692 for a channel which is V-shaped in cross-section.The gas from feed 250 connected to tube 256 is directed upward andoutward by the channel formed between the baffle 400 and support 692.The gas exits the channel near the circumference 49 of water 48. Thewafer 48 is located between the top of baffle which has its cone pointeddownward and a transparent vacuum wall 238. A heating module 694 islocated above the wall 238.

FIG. 25B shows a more detailed view of a process module 695 which issomewhat similar to that of FIG. 25A. These two embodiments differprimarily in that the wafer is heated, in FIG. 25A, by a radiant heatingmodule which illuminates the wafer through the transparent vacuum wall238 or alternatively, which illuminates a silicon susceptor which thewafer is pressed against, whereas in FIG. 25B it is simply a resistivelyheated susceptor 252.

In FIG. 25B, the gas flow of activated species from remote plasmachamber 254 (FIG. 25A) is connected to a funnel shaped gas distributor416 by a slip-fit joint 258 (similar to that shown in FIG. 9) betweenthe funnel shaped gas distributor 416 and the feed 250. The slip-fit 258is provided to accommodate the upward and downward movement of theprocess module 295 which open and close the process chambers of thevarious modules disclosed herein. The feed 250, which is an extension oftube 256, can be, as described above, a quartz tube which does not moveas the reactor opens and closes. A bellows 414 encloses the slip-fitjoint, to make it effectively gas-tight without requiring any slidingjoint which might introduce particulates, but alternatively a slip-fitjoint like that shown in FIG. 14 which is merely vented to the exhaustspace could be used instead.

The generally conical baffle 400 is supported inside the funnel shapedgas distributer 416 by small protrusions (not shown) to define a channelor flow path 408 which is about 1 mm thick. Spring pins 406, mounted onthe funnel shaped gas distributor 416, hold the wafer 48 against theheated susceptor 252, which is preferably shaped to include a recess 412which is about 0.5 inch deep around the circumference 49 of the wafer48. This recess 412 facilitates removal of the backside bead. Whenphotoresist is spun on (i.e. deposited as a liquid onto a spinningwafer), the resulting edge bead will normally extend around the wholeedge of the wafer, front and back, even though resist is not coated ontomost of the area of the backside, and removal of this backside bead is asignificant difficulty in dry processing methods for edge bead removal.A ring-shaped protrusion 404, surrounding the recess 412 in thesusceptor, further assists in enhancing the dwell time of activatedspecies near the circumference 49 of the wafer. This edge bead is asource of particles during handling and processing.

The choice of temperature is determined by the type and state (baked orunbaked) of the photoresist. Higher temperatures yield faster rates.Changing the process chemistry can, however, significantly compensatefor lower temperature processing. For processing patterned, unbakedresist films of conventional type, it was found that the maximumtemperature for operation was 100 C. Above this temperature the resistbegan to flow, ruining pattern definition.

The flat or base side 420 of the conical baffle 400 is held close to thewafer 48 during the processing operations. The radius of the base side420 of conical baffle 400 is about 1 mm less than the radius of thewafer 48. The conical baffle 400 is usefully fabricated from aluminumwhich has been hard anodized over its entire surface except for its flatbase side 420. This flat base side 420 is reactive enough to help getteractivated species which diffuse in past the edge of the flat base side420 and which therefore might erode the resist material in more centralparts of the wafer 48.

Even with the native oxide present this aluminum face still hassubstantial ability to scavenge oxidizing species such as ozone ormonatomic oxygen which diffuse in past the edge of the distributor, sothat the edge-preferential selectivity of the operation is improved.

Edge selectivity is further enhanced by bleeding a purge gas supplied atconnection 410 through vent line 402, which runs through the conicalbaffle 400 to exit in the narrow space (e.g., about 1 mm high) betweenthe base side 420 of the conical baffle 400 and the wafer face 54.

To accelerate the reaction rates, the susceptor 252 is heated to atemperature of at least 100 C. Temperatures of 120-130 are useful forconventional resist materials, but the choice of temperature will dependon the particular process conditions. For example, resist materialswhich have a higher reflow temperature will generally permit a highertemperature.

Edge bead removal may also be useful, in some processes, as a stepperformed after ashing has removed the resist from most of the wafer'sface where total removal of resist is the desired end, and aparticularly stubborn edge bead remains after the rest of the resist hasbeen removed, the structure of FIG. 25B may optionally be operated athigher temperatures such as 300 C.

A sample process recipe which has successfully demonstrated photoresistedge bead removal is as follows: in a reactor configuration like thatshown in FIG. 25B, a process gas flow of 1000 sccm O₂ plus 200 sccm H₂and 1 Torr total pressure was activated by a 400 W microwave dischargeupstream of the wafer, while the susceptor 252 was held at 100 C. In 120seconds this sample process embodiment successfully removed the edgebead (estimated to be about 3 microns thick) which resulted fromspinning on a 2 microns thick coat of photoresist. The heat appliedduring this time also accomplished the "soft bake" which is well knownas a useful step in photoresist processing.

FIG. 26A shows a sample embodiment for a single wafer sputtering systemwith in situ cleanup for wafers 48, which includes, unlike any of theembodiments described thus far, not only the top chamber 218 below thewafer 48, but also an upper process space 430. The top chamber 218 isused for in situ cleanup, and the upper process space 430 is used forsputter deposition, but other uses of this system's capability arepossible.

This sample embodiment also differs somewhat in the wafer transportused. The wafer transfer arm 28 places the wafer 48 down onto threesupport fingers 214 (only two of which are shown in FIG. 26B and FIG.26C) which are mechanically supported from below, such as the threesupport fingers 214 (FIG. 12). The wafer 48 would have been placed ontofingers 214 by the arm 28 as discussed above. The fingers 214 are thenmoved upward until the wafer 48 contacts the susceptor 438 and thechamber is sealed. One or more seals 911 is located between the thesusceptor 438 and the top of vertical exterior wall 913 (as shown inFIG. 26B) of chamber 218. A process step can then be carried out in thetop chamber 218 (FIG. 26A) if desired. Three fingers 440 (only two ofwhich are shown in FIGS. 26B and 26C. The fingers 440 extend downward(as shown in FIG. 26B) around the pivotable susceptor 438. The fingers440 could alternatively extend through the susceptor 438. The fingers218 and 440 would be spaced at 120 degree intervals about the samevertical axis although the fingers 218 and 440 would be offset from eachother about the axis. When motor or solenoid 910 is actuated the fingers440 move upward along the vertical axis and engage the wafer 48 atlocations adjacent is circumference 49. Face 54 of the wafer 48 isfacing downward and the fingers 440 engage the face 54 close to thecircumference 49.

A support 912 (FIGS. 26 B and C) is attached to susceptor 438 and toanother motor 920 (FIG. 26A). The motor 920 is mounted on the outside ofthe process module 914 and is connected through a vacuum seal 922 (FIG.26A) to support 912. Thus, suppport 912 is rotatably attached to thegeneral support structure of process module 914 (FIG. 26A) and rotatesabout the axis 916 (FIG. 26A). When support 912 rotates about axis 916in a counterclockwise direction as shown in FIG. 26B it moves theposition shown in FIG. 26C which is 90 degrees form the position shownin FIG. 26B. The susceptor 438, solenoid 910, and wafer 48 are alsorotated. A shutter 918 is located to selectively cover the sputtertarget 432. The shutter 918 is shown in the close position in FIG. 26Band in the open position in FIG. 26C and FIG. 26A. The shutter 918 isrotated by a motor 924 (FIG. 26A) between its open and closed positions.Motor 924 is mounted on the outside of process module 914 and isconnected through a vacuum seal 926 to the shutter 918.

After the wafer is transferred onto fingers 214 by arm 28 and the arm isretracted, the fingers 214 are moved upward to clamp wafer 48 tosusceptor 438. This is the position shown in FIG. 26B. While the waferis in the horizontal position shown in FIG. 26B, a cleanup operation,for example, can be performed, e.g. by flowing a CF₄ plus O₂ mixturethrough a remote plasma and also optionally providing ultravioletillumination in situ from a plasma which is remote from the wafer face,as discussed above.

After the above operation, the fingers 440 move upward and clamp waferto susceptor 438. The fingers 214 are then lowered and the top chamber218 opened. The susceptor is rotated counterclockwise from the somewhathorizontal position shown in FIG. 26B to the somewhat vertical positionshown in FIG. 26C by motor 920 (FIG. 26A). The wafer 48 is transferredto process space 430 by pivoting the susceptor 438 using motor 920.After the wafer is in its upper or vertical position, as shown in FIG.26C, a shutter 918, which, for example, can be pivoted on another axis,at right angles to the axis on which the pivotable susceptor 438, isused to ensure isolation from the top chamber 218.

After the wafer 48 is rotate to the vertical position shown in FIG. 26C,the sputter module 930 can be powered up momentarily to clean the targetby sputtering onto the shutter 918, while the shutter 918 is in itsclosed position as shown in FIG. 26B. The shutter 918 is then retractedto its open position as shown in FIG. 26C. Sputter deposit accomplishedunder fairly conventional conditions. The upper chamber is then held ata pressure of less than 100 mTorr (e.g. 30 mTorr), the shutter 918 isrotated to uncover the sputter target 432, and a potential of 1000 V isapplied between the cathode 436 (FIG. 26A) and the sputter target 432.To enhance deposition efficiency, a smaller bias (e.g. 200 V) can beapplied between the wafer 48 and the sputter target 432. After thesputter operation is completed the shutter is closed and the susceptor438 and wafer 48 are rotated to the position as shown in FIG. 26B.

If it is desired to perform a process in the top chamber 212, thefingers 214 are raised and the top chamber 212 is closed. Then thefingers 440 are lowered. The desired process is performed, for example,a cleanup process. The wafer can then be transferred from the processmodule 914 by an arm 28 as described above in connection with FIGS. 1,3, and 4.

In the alternative the wafer can be transferred from the process module914 transfer arm 28 can enter into the process module 914 after thesusceptor 438 is rotated clockwise to the position in FIG. 26B. The armcan after being positioned below the wafer 48, be moved vertically untilthe pins 50 (FIGS. 1 and 3) are in contact with the wafer 48. Thefingers 440 are then lowered and the arm 28 lowers slightly and exitsthe process module 914. The pressure during the sputter should be lessthat 200 mTorr.

FIG. 27 shows a process module 940, which has the capability ofprocessing several wafers 942, similar to wafer 48, simultaneously. Achamber 12 and an arm 28 as discussed in FIGS. 1, 3, and 4 transfer thewafers from a carrier shown in FIG. 1 to the process module 940. Theprocess module 940 has a steel outer jacket 944, which is adapted towith stand high pressure, for example, 100 atmospheres. The jacket 944can be made, for example, of 300 series stainless steel. The wafers 942are placed into the process module 940 by an arm (not shown) similar toarm 28 (FIGS. 1, 3, and 4). The wafers are places into slots 946 ofquartz rods 948. The quartz rods 948 extend vertically through the topchamber 950. Although only two rods 948 are shown in FIG. 27, additionalrods can be provided, for example, a rod positioned on the right side ofthe chamber 950 to engage the wafers 942 as positioned in FIG. 27. Thedistance between the slots 946 can be sufficient to allow the arm toreach into the stacked wafers 942 to extract. In the alternative, thebottom slot of slots 946 can be a sufficient distance from the bottom952 of chamber 950 that the arm can place the bottom most wafer. Thewafers 942 can then be placed from the top slot into each of theintermediate slots with the bottom slot filled last.

The interior wall 957 of chamber 950 and lower chamber 955 are made ofquartz. The space between the jacket 944 and interior wall 957 isequalized with the pressure in chamber 950 during the high pressureoperation in order to minimize the stress on the interior wall.Controlled check gas valves 960 and 962 which are connected to the spacebetween the jacket 944 and interior wall 957, and chamber 950,respectively, are used by the computer control system 206 to control thepressure so that the stress of the pressure differential on the interiorwall 957 does not become too great by venting excess pressure asrequired. For example, if the pressure within chamber 950 becomesgreater than the pressure in the space between jacket 944 and theinterior wall 957, the system 206 operates valve 962 and releasespressure until the pressures are at an appropriate level, for example,about equal.

Bottom 952 has a plurality of holes 965 which allow gas supplied to thelower chamber 955 to move upward into chamber 950 above. The gas to thelower chamber 955 is supplied through pipes 970 thru 972. The pipes970-972 can be made of any suitable material. Pipes 970 and 971 supplyprocess gases at high pressure (100 atmospheres) to lower chamber 955which are used within chamber 950 to perform the desired process. Pipe972 supplies a purge gas to the space between the jacket 944 andinterior wall 957. The necessary vacuum is supplied to chamber 12 bypump 975, chamber 955 by pump 976, and chamber 955 by another pump (notshown) through pipe 978. The process chamber 950 of process module 940unlike the other process modules shown herein does not seal by movingthe wafer upward into a top chamber. In module 940 the process chamber950 is sealed and unsealed by moving a vertical section 980 of theinterior wall 957 upward and downward utilizing bellows 981. In the openposition the transfer arm 28 similar to arm 28 has access to chamber 950to transfer wafers 942 through port 30 when gate 31 is open (as shown inFIG. 27). The processing takes place when the chamber 950 is closed. Aheater 982 is located on the interior wall 957 within the chamber 950 toapply heat for the process being conducted within chamber 950.

In operation, carrier 10 is opened and the wafers 947 are transferredfrom carrier 10 into chamber 950 under vacuum (as discussed above withreference to FIGS. 1, 3, and 4). The gate 31 is then closed. Gas issupplied into the space between the jacket 944 and the interior wall 957and the chambers 950 and 955 from pipes 970 and 971. The chamber 950 isthen closed and the processing is performed at high pressure with gassupplied through pipes 970, 971 and 972 which can be, for example, O₂,Hydrogen, and Nitrogen, respectively. Heat from heater 982 can beapplied as desired. After the processing over and the gas from pipes 970and 971 is discontinued, the chamber 950 is purged by gas from pipe 972,for example N₂. The chamber 950 is then brought to the desired vacuum. Avacuum process can then be performed if desired. The chamber 950 isopened and the wafers transferred through port 30 to carrier 10. Thecarrier 10 will be closed as discussed above with reference to FIGS. 1,3, and 4. Although the module 940 is shown as capable of accepting 5wafers the module can be adapted to provide for more or less. Less than5 wafers can be processed at a time, for example, one wafer.

A high pressure process module which is compatible with a system whereinintegrated circuit wafers are largely transported and processed undervacuum. The pressure vessel can be extremely small, for example, 0.2liters i.e. has a total pressurized volume of which almost all interiorpoints are within one or two centimeters of one of the wafers which maybe loaded into the chamber.

The module 940 has other uses such as slow processes which are reactionlimited such as oxide growth where it is useful to have several wafersprocessed simultaneously. This can be done as desired without the gasbeing applied from pipes 970-972. Thus this module 940 is adapted toprocess Application Specific Integrated Circuits.

The mechanical strength constraints of high pressure operation areeasier to design for. This also means that pressurization and vent downof the high pressure module can be performed more rapidly. Also, thecapability to perform high pressure processing (e.g. high pressureoxidation) in a module compatible with a vacuum processing system,increases throughput and eliminates the need to perform necessaryoxidation steps external to a vacuum processing system.

This class of embodiments provides the capabilities of a conventionalfurnace (which is normally a high-particulate operation), whileadvantageously allowing compatibility with a low-particulate vacuumprocessing system. Moreover, this class of embodiments advantageouslyprovides the capabilities of a conventional furnace (which normallyrequires a relatively large amount of floor space and plumbing) in avery compact area.

In an example of the use of process module 940, HgCdTe can be processedto form passivation layers using gas phase oxidation or sulfidization athigh pressure. The HgCdTe substrates are heated to 50 between 150degrees C. and a thin oxide film formed. A source of sulfur, forexample, H₂ S, can be supplied from pipe 970 at, for example, 100 sccmat a pressure of 50 to 100 atmospheres. A thin sulfide insulating filmwould be formed. It is also possible to provide oxidation by usingoxygen at, for example, 100 sccm and hydrogen at 40 sccm, for example,to produce a water vapor/oxygen mixture at a pressure of 10 to 100atmospheres.

FIG. 28 show a process module 1000 which is adapted for use as animplanter. An implanter is utilized to place or implant dopants into thesurface of a wafer, for example, wafer 48. The wafer 48 is placed intothe module 1000 by an arm (not shown) similar to arm 28 discussed abovewith reference to FIGS. 1, 3, and 4. The chamber 12 and carrier 10 areutilized above as discussed with reference to FIGS. 1, 3, and 4. Avacuum pump 1002 and a valve 1004 are connected to the interior ofmodule 1004 to provide the required vacuum. Other pumps and valves canbe provided as necessary.

The wafer 48 is placed into the top chamber 1006 by the arm (not shown)from carrier 10 through chamber 12 and a port (similar to port 30 inFIG. 3). The wafer is placed onto fingers 214 which can be constructedfrom hard-anodized aluminum or silicon so that the fingers areconductive. The top chamber 1006 is closed by the upward verticalmovement of a bellows 1008. The fingers 214 raise the fingers 214 untilthe wafer contacts an electrode 1010 in the upper portion of chamber1006. This is the position of wafer 48 shown in FIG. 28. Gas, whichcontains the substance to be implanted into the downward face 54 ofwafer 48, enters a heating chamber 1012 thru a pipe 1014 from a gassource (not shown), for example, As. Within the heating chamber 1012 thegas from pipe 1014 is heated to the appropriate temperature for theparticular dopant, for example, 350 degrees C. for Arsenic and 280degrees for Phosphorus. The gas then flows upward into a microwavecavity 1020 through a pipe 1022. An additional gas can be introducedinto the cavity 1020 through a pipe 1024, for example, He or Ar. Alsoadditional gases, for example, BF₃ for use as a p-type dopant can befeed through pipe 1024. The gas is subjected to microwave energy withincavity 1020. The gas becomes free radicals within cavity 1020 with apressure of, for example, 0.1 Torr. The gas exits the cavity 1020 andpasses through a pipe 1026 into a lower chamber 1028 located below topchamber 1006. The pipe 1026 passes through the central portion of achamber 1030 below lower chamber 1028. The chamber 1028 is partiallysurrounded along its vertical axis by bellows 1008.

The gas passes upward from the lower chamber 1028 through a quartzshower head 1032 into top chamber 1006. Shower head 1032 extendshorizontally between top chamber 1006 and lower chamber 1028. The showerhead has a number of openings 1036 which allows the gas in lower chamber1028 to pass into chamber 1006. The shower head is a part of a quartzbaffle 1040. The baffle 1040 is a cylindrical shape with its axisextending vertically through the central portion of chambers 1006 and1028 with the shower head 1032 extending horizontally. The shower head1028 can be of the type shown in FIG. 30C, if desired. Within chamber1006, the gas is accelerated toward wafer 48 to implant the substance inthe gas into the face 54. The ion current must be adjusted according tothe pressure within the chamber 1006. Two bias plates 1042 and 1043 arelocated around the baffle 1040 outside chamber 1006. The plates 1042 and1043 have negative and positive voltages, respectively, applied. Plate1042 is located below and is separated from plate 1043. A magnet 1048 islocated just above the plate 1043. Generally, the magnetic field needsto be of sufficient strength to repel the free electrons from the wafersurface 54. A positive voltage is applied to electrode 1010, forexample, 100 to 10,000 volts. The free radicals are controlled withinthe chamber 1006 and are accelerated toward and into the wafer 48. Theelectrode 1010 can be cooled by passing fluid through openings 1034, ifnecessary.

The process module 1000 which is compatible with a system using vacuumwafer transport in which wafers are generally transported and processedin a face down position under vacuum.

The process gas lines 32 and the other feeds, gas lines, and pipes suchas pipes 970 thru 972 shown herein are formed (or coated) to have tinygrooves on their inner surfaces or riblets to reduce particleentrainment at the surface. The use of riblets on the exterior of an airvehicle for reducing drag has been suggested by "Grooves Reduce AircraftDrag", NASA Technical Briefs 5(2), page 192 (1980), and "MissionAccomplished". NASA Technical Briefs 11(3), page 82 (1987). However, inthe present invention riblets are used to stabilize a stagnant boundarylayer on the walls of the piping, and therefore reduce the chance thatthe gases flow through the piping will exert sufficient pressure on aparticle adhering to the walls to detach it. For any given degree ofcleanliness of process gas source, this advantageously reduces thenumber of particles which are transported into the process chamber whileentrained in the gas.

Several embodiments of the shape and size of these riblets are shown inFIGS. 29A, 29B, 29C, 29D, 29E, 29F and 29G. Although the NASA TechnicalBriefs cited suggest the use of riblets on the exterior of air vehicles,it is an advantage of the present invention that it utilizes thesegrooves or riblets to reduce the chance that gases flowing throughpiping will exert sufficient pressure on a particle adhering to thewalls to detach it. The NASA publications indicate that the groovesconfine incipient bursts of turbulence so that they cannot expand anddisrupt the boundary layer surrounding a moving aircraft. As shown inFIGS. 29A-G, most embodiments of the grooves are generally V-shaped, butthey may take a variety of configurations. For example, they may haverounded or sharp peaks in symmetrical or asymmetrical cross sections.Asymmetrical grooves of various cross sectional geometries may bearranged in some regular sequences to optimize the aerodynamicperformance. Thus, in the present invention, these grooves or ribletsare used to stabilize a stagnant boundary layer on the walls of thepiping. For any given degree of cleanliness of process gas source, thisadvantageously reduces the number of particles which are transportedinto the process chamber while entrained in the gas. Although only oneor two grooves or riblets is shown in each of the drawings 29A-29G, manysuch grooves or riblets would be included as a part of the interior wallthe pipes, feeds, distributors etc. shown in connection with the processmodules disclosed herein.

FIG. 29A shows a V-shaped groove 1100 in the wall of pipe 1102. Only apart of the pipe 1102 is shown in a cross-section taken across a part ofthe interior wall of the pipe, which is true of the other pipes in FIGS.29A thru G. The groove 1102 can be 0.010 inches deep and 0.045 incheswide from peak 1104 (on the left in FIG. 29A) to peak 1006 (on the rightin FIG. 29A).

FIG. 29B shows another V-shaped groove 1110 in the wall of pipe 1112.Groove 1110 is in the range of 0.010 to 0.020 inches wide between peaks1114 (left) and 1115 (right) and has a depth of about 0.020 inches.

In FIG. 29C. a protrusion 1120 extends from the interior wall of pipe1122. The protrusion 1120 has a triangular cross-section with a 90degree angle at the peak 1124 and a 30 degree angle at its base on theleft and a 60 degree angle at its base on the right. The distance fromthe peak 1124 to the base can be, for example, 0.01 inches and thedistance across the base can be, for example, 0.023 inches. The groovesor riblets would be formed between the various protrusions. Anotherprotrusion 1150 in a pipe 1152 is shown in FIG. 29F with the same basicshape as protrusion 1120. Protrusion 1150 has the same angles with adistance across its base of, for example, 0.046 inches and a height fromthe base to its peak 1154 of, for example, 0.02 inches.

Another triangular protrusion 1130 is shown in FIG. 29D. Protrusion 1130has a 60 degree angle at its peak 1132 and a 40 degree angle at its baseon the left and an 80 degree angle at its base on the right. Theprotrusion extends from the interior wall of pipe 1134. The distanceacross the base of the triangular shape can be about 0.028 inches withthe distance from the base to the peak 1132 about 0.020 inches. Anotherprotrusion 1160 in a pipe 1162 is shown in FIG. 29F with the same basicshape as protrusion 1130. Protrusion 1160 has the same angles asprotrusion 1130 with a distance across its base of, for example, 0.028inches and a height from the base to its peak 1164 of, for example, 0.02inches.

FIG. 29E shows a V-shaped groove 1140 in the interior wall of pipe 1142.The distance between the peaks 1144 (left) and 1145 (right) can be, forexample, about 0.010 inches. The peaks 1144 and 1145 are rounded. Thegroove 1140 can be, for example, 0.020 inches deep.

One class of processes which has shown very significant success inreactors of the kind described above is anisotropic fluorine etches formaterials including refractory metals.

It has been found that a combination of a hydrocarbon with a brominesource, for example, HBr or CF₃ Br, provides a very potent passivatingchemistry for fluorine-based etches. A fluorine source such as SF₆, NF₃,HF, F₂, CF₄, C₂ F₆, BF₃ or SiF₄ can be used for the fluorine-based etch.For example, one embodiment which has been successfully demonstrated isas follows: The starting structure included a thin film of tungsten.Initial gas flows included 50 sccm of SF₆. 5 sccm of CH₄, and 15 sccm ofHBr, at a total pressure of 250 milliTorr and an applied RF power levelof 500 Watts. After the pattern had begun to clear, an additional flowof 20 sccm of WF₆ was added, as will be further discussed below. Theresulting structure showed nearly vertical etched sidewalls, only slightlinewidth erosion, and excellent selectivity to resist. In anotherprocess, a source of Fluorine with WF₆ acting as a load during overetchhas been found to reduce line width loss.

By increasing the fraction of CH₄ and also that of the bromine source,even more robust passivant action can be achieved. The followingconditions produce were found, for example, to produce zero linewidtherosion: 40 sccm of SF₆, 15 sccm of CF₄, and 25 sccm of HBr, at a totalpressure of 470 milliTorr and an applied RF power level of 400 Watts.The use of relatively high total pressure assists in maintaininguniformity.

If the rate of passivant deposition is increased still further, negativeetch bias can be achieved. In a sample embodiment, a thin film oftungsten was etched using the following initial gas flows: 50 sccm ofSF₆, 18 sccm of CF₄, and 25 sccm of HBr, at a total pressure of 470milliTorr and an applied RF power level of 400 Watts. The resist patternused had 2.7 micron minimum pitch (1.7 micron minimum line width and 1micron minimum space width). The use of this chemistry was found toproduce finally etched space widths of 0.6 to 0.7 microns. Thus, thischemistry provided a "negative etch bias" of approximately 0.15-0.2micron. As an upper limit, further experiments demonstrated thatincreasing the flow of methane to 21 sccm, without changing the otherconditions, shut down the etch entirely, i.e. the tungsten etch ratewent to zero.

It has also been discovered that this class of passivating chemistriesprovides a highly anisotropic silicon etch. One specific sampleembodiment, which was successfully demonstrated by experiment, used anetch chemistry as follows: Initial gas flows included 50 sccm of SF₆, 5sccm of CH₄, and 15 sccm of HBr, at a total pressure of 250 milliTorrand an applied RF power level of 500 Watts.

These conditions etched 3 microns deep into silicon in 25 seconds, andproduced an approximately vertical silicon sidewall while maintainingexcellent selectivity to resist. However, these etch conditions are notparticularly selective to oxide. Thus, this etching chemistry isextremely useful for etching trenches. The advantages of trenches indevice structures have long been recognized, but they have usually beenfabricated by low-pressure etching conditions which are slow and areprone to produce very undesirable etching artifacts such as retrogradebowing, grooving, or asperities on the bottom of the trench. It is alsoan advantage of the avoiding these difficulties of low-pressureprocessing.

Another, alternative, family of chemistries for fluoro-etching uses afeed gas mixture which includes a fluorine source such as SF₆) plus abromine source, such as HBr, plus a very weak oxygen source (e.g.,carbon monoxide). This chemistry provides anisotropic high ratefluoro-etching with good selectivity to photoresist.

A sample embodiment of the process discussed has been successfullydemonstrated as follows: The starting structure included a thin film oftungsten covered by a patterned layer of developed organic photoresist.Initial gas flows included 25 sccm of SF₆, 25 sccm of HBr, and 40 sccmof CO, at a total pressure of 300 milliTorr and an applied RF powerlevel of 175 Watts. During the overetch period an additional flow of 20sccm of WF₆ is usefully added. The resulting structure showed steeplysloped sidewalls, only moderate linewidth erosion, and approximately 2to 1 selectivity over photoresist.

This chemistry could be modified by substituting another weak oxygensource for the carbon monoxide. That is, weak oxygen sources such as N₂O or CO₂ could be used instead. In fact, it would even be possible toderive some benefit by using an extremely small flow (less than onesccm) of O₂ in place of the CO, but such very small flows are difficultto control reproducibly with conventional semiconductor manufacturingequipment.

Another, alternative, family of chemistries for fluoro-etching uses afeed gas mixture which includes a fluorine source (such as SF₆) plus afluorosilane (e.g., SiF₄), plus a bromine source (such as HBr), plus aweak oxygen source such as carbon monoxide. This chemistry providesanisotropic high rate fluoro-etching with good selectivity tophotoresist.

A sample embodiment of this process has been successfully demonstratedas follows: The starting structure included a thin film of tungsten,covered by a patterned and developed layer of organic photoresistmaterial. Initial gas flows included 25 sccm of SiF₄, 25 sccm of SF₆, 25sccm of HBr, and 30 sccm of CO, at a total pressure of 350 milliTorr andan applied RF power level of 175 Watts. During the overetch period anadditional flow of 30 sccm of WF₆ is added to the other flows described,to avoid resist erosion. The resulting structure showed nearly verticaletched sidewalls, only light linewidth erosion, and approximately 3 to 1selectivity to the photoresist.

A two-stage showerhead 280 (FIG. 30C) is placed between the end of thethird gas feed 250 and the top chamber 218 near the lower face 54 ofwafer 48. An example of such a showerhead is shown in FIG. 30C. Twobaffles 284 and 286, held horizontally in fixed relationship within ahousing 282 with baffle 286 located below baffle 284. Third gas feed 250is located below baffle 286 and the gas passes upward from the gas feed250 through holes 290 in baffle 286 and openings 1202 in baffle 284.Both baffles are both placed to block the flow of the process gases fromthe third gas feed 250 into the wafer top chamber 218, and the twobaffles are aligned so that no hole 288 in the second baffle 284 isdirectly aligned with any hole 290 in the first baffle 286. The showerhead 280 can be utilized as desired with the process modules disclosedherein. The housing 282 can have several shapes and can for example havea funnel shape with the narrow portion of the funnel located around thefeed 250 and the baffles located above in the cylindrically shapedportion of the funnel.

The two-stage showerhead is, in this embodiment, made of "tuframcoated"(a Teflon-impregnated (TM) anodized) aluminum. Teflon, or quartz.Successful experiments have demonstrated that some other showerheadgeometries also work (e.g., a quartz tube with a circular ring, with gasdispersion holes placed away from the wafer), but the two-stageshowerhead is more useful due to its high throughput and uniformity.

As remote plasma processing is relatively new, prior methods of dealingwith nonuniformity are few. One manufacturer has used a singleshowerhead with fairly large holes (about 0.25" i.d.) in two concentriccircles, with one smaller hole (about 0.15" i.d.) in the center.Although this is an improvement over no showerhead, as another anothercommercial photoresist stripper is set up, significant higher strippingrates still occur at the center of the wafer. The pattern of resistremoval visibly copies the pattern of holes in the showerhead. A plot ofresist removal across the wafer is shown in FIG. 30A. For comparison,results without any showerhead are shown in FIG. 30B.

The curves in FIG. 30B show that as the distance from the center of thewafer increases the amount (thickness) of the resist removed decreases.The curves in FIG. 30A show that the use of the two stage shower headgreatly improves the uniformity of the resist removal.

The failure of the single showerhead is due to the nature of the gasflow in the reactor. The flow is viscous and laminar, resulting in avelocity profile across the tube that goes as ##EQU1## Near the tubewall (r=R) the gas velocity is very low, while at the center of the tube(r=O) the gas is moving much faster, up to twice the averagevelocity,<v>. When gas with such a velocity distribution impinges on thewafer, more reactants will be transferred where the velocity is high,rather than where it is low. This causes the observed nonuniformity, butthe embodiments disclosed here solve this problem.

The solution lies in reducing the difference in velocity from one pointto another in the gas stream. This must be done downstream of thedischarge tube, where the reactor cross section is large, so that thegas flow will not return to the steady state given by Equation 1 beforereaching the wafer. Since gas passing directly through a showerhead holewill not have its velocity significantly changed, no gas parcel may beallowed a direct or "line-of-sight" passage from the discharge tube tothe wafer. If any line-of-sight passages remain, gas will passpreferentially through them.

To prevent line-of-sight passage, a second showerhead or baffle isrequired. The essential feature of this baffle is that it block directflow of gas from the discharge tube through the lower showerhead, asshown in FIG. 30C. By doing so, gas parcels will become sufficientlymixed so that a relatively uniform velocity profile will emerge belowthe lower baffle. The first showerhead component encountered by theflowing gas may consist of (1) a number of connected baffles to blockdirect passage of gas through the second showerhead component; or (2) asingle solid baffle to completely arrest forward motion, forcingvelocity vectors to change from the axial direction to the radial,before encountering the second showerhead component: or (3) a structureintermediate between (1) and (2).

The results of using another shape for the baffles and housing is shownin FIG. 30D. The curves in FIG. 30D shows the improved, but not yetoptimized, ashing uniformity that resulted from an implementation of thetwo-stage showerhead concept, where the first showerhead consisted of aconical baffle just covering the central hole in the second showerhead.This can be compared to FIG. 30A, which was obtained using the secondshowerhead without the baffle even though the specific chemistryemployed was different. This shower head can have a baffle like baffle284 shown in FIG. 30C. It can also have a lower baffle which is a coneposition just above the end of feed 250 with the point of the conedirected upward. The diameter of the cone can be just greater than thediameter of the feed 250. It is also possible to invert the cone. Othertwo shower head arranges are possible.

The chamber walls need to lie sufficiently far from the showerhead andwafer so that subsequent slowing of gases along the wall does notsignificantly affect the newly developed gas velocity distributionbefore the wafer is reached. The effect of this uniform velocitydistribution is to create a uniformly thick boundary layer of thicknessd over the surface, as shown in FIG. 30E, taken from H. Schlichting."Boundary-Layer Theory." (7th ed. 1979). which is hereby incorporated byreference. A uniform boundary layer will lead to uniform transport ofreactants to the wafer.

The material forming the showerhead may be of ceramic, hard anodizedaluminum, stainless steel, Teflon, or quartz--the choice depending oncompatibility with process gases. The dimensions can be chosen to fitany wafer size, provided that the reactor wall be far enough from thewafer not to affect the uniform velocity profile. The size of holesshould be reasonably large (probably 0.1"-0.25") so as to notsignificantly impede overall gas throughput or cause loss of reactivespecies on its surface, and to assist in machining. The distance betweenthe two showerhead pieces should be at least as large as the holediameter. The two showerhead parts may be oriented for face-downprocessing.

Thus, this class of embodiments provides the following advantages: (1)application to all isotropic processing in fast flowing remote plasmasystems. (2) promotion of uniform processing results, (3) maintenance ofhigh reactant throughput for high rates of etching and deposition, (4)flexible materials choice for process compatibility, (5) comprehensionof face-down processing.

Some relevant background information may be found in the article by C.J. Howard at vol. 83, J. Phys. Chem., page 6 (1979), which is herebyincorporated by reference.

One process disclosed herein provides a descum process which is aprocess for removal of polymers and other organic residues. The processuses a remote plasma, supplied through a distributor which includes atwo-stage showerhead (FIG. 30C), to achieve improved results.

A general processing requirement when using photoresists is a stepreferred to as "descum." Normal photoresist processing does not providea totally clean pattern after the resist has been exposed and developed.There are areas in the pattern which are desired to be cleared and stillcontain a significant residue of high-molecular-weight polymericcompounds. Normally, these must removed by an aggressive isotropic etch.For example, a layer of photoresist which is 1.4 microns thick inunexposed areas may still contain resist residues of 0.5 micron or morein the areas which need to be cleared. Conventionally this is done as awet processing step, but the embodiment disclosed here provides a way toperform this function in a dry process.

In one embodiment of this process, descum of patterned photoresist wassuccessfully demonstrated using a process mixture of 1000 sccm O₂, 200sccm H₂ at 100 C. and 1 Torr total pressure. The choice of mass flowswas set to result in a high removal rate, proportional to O₂ mass flow,but retaining uniform removal across the wafer which is inverselyproportiona; to mass flow and pressure. The reactor is set up with allgases passing through a remote plasma chamber 254 powered at 400 W.

The process chemistry can alternatively consist of O₂ plus one or moreof the species: N₂ O, H₂ O, H₂, CF₄, CHF₃, HCl, HBr, and Cl₂. Of these,H₂ is the most useful in some instances additive gas for the followingreasons: (a) the N₂ O additive does not enhance the rate as much as H₂,particularly at lower temperatures: (b) halogen-containing gases presentsome risk of deleteriously affecting the metals present on thesubstrate. If this constraint were lifted, CF₄ and CHF₃ would be verygood choices, because they could provide descum rates as much as oneorder of magnitude faster than H₂. The remaining problem with CF₄ andCHF₃ is reactor materials-compatibility problems due to the presence ofF atoms. This could be solved by using a Teflon ™ showerhead.

The hydrogen species used may be participating advantageously in thereaction by assisting in the opening of unsaturated bonds in the resistmaterial.

Selectivity is not tremendously crucial in descum processes, but in factthe process described does have good selectivity to silicon, which is anadvantage.

The resist used was standard positive resist. In the test examplespecified, Shipley 1813 ™ resist, which had been developed with anMF-314 developer, was used. Patterning was performed at an i-linewavelength, for about 250 msec. to give "scum" due to underexposure. Theresist was on bare Si, for the purpose of study, but in actual use theprocess would be carried out with photoresist on top of a film to beetched, e.g., aluminum. The sample was processed to leave a substantialamount of unexposed photoresist between desired patterns. In fact, it isestimated, by measurements of SEM pictures, that there was as much as5000 Ångstrom of photoresist remaining between desired resist patterns,which is at least an order of magnitude worse than what would likely beencountered in a real life case. In the present case, the intermediate"scum" was removed in 6 min, according to optical microscopy. Thus, in areal case, with more like 500 Å of scum typically present, processingshould take less than 1 minute.

A general problem with processes which use a remote plasma to generateactivated species for etching or deposition applications is poor processuniformity across the surface of the wafer. This is a consequence of gashydrodynamics which causes the formation of a boundary layer of stagnantgas just over the surface of the wafer. The stagnant gas hampers thetransfer of reactants and products to and from the wafer. The problemsare exemplified in photoresist ashing, where resist removal is typicallyseveral times higher immediately under the discharge tube's entrance tothe reaction chamber than at the edge of the wafer. In this instance,the poor uniformity frustrates the use of such equipment for descummingapplications. The teaching in the present application of using aspecially designed two-stage showerhead will as a gas distributor inremote plasma applications provides the advantage of greatly improveduniformity.

Referring now to FIG. 31, there is depicted a block diagram of theelectrical instrumentation and control system 700 for a vacuumprocessing system. This system can be controlled by a computer controlsystem 206 which could be an 8088-based PC, or specifically, a TexasInstruments Professional Computer. The computer control system can beprogrammed to perform a specific processing sequence upon demand. Oncethe process is initiated, the computer control system 206 monitors andcontrols the process flow.

The system has a number of process monitoring instruments which provideinput signals to the control system 206 and based upon those inputs andthe proprogrammed process sequence, the control system 206 providesoutputs either to controllers or directly to specific components. Eachof the inputs and outputs of computer control system 206 will bedescribed below.

After the the vacuum wafer carrier 10 (FIG. 1) has been placed in thevacuum load lock chamber 12 and shut the load lock lid 20, he thenbegins the automated process sequence. Keyboard interaction with thecomputer control system including process sequence and start is menudriven. During the initial start up sequence, before the actualprocessing has begun, the roughing pump, turbo molecular pump, and ifnecessary a cryogenic vacuum pump are all started.

The purge and pump down functional sequence is shown on FIG. 11 andreference is made to it where appropriate. When the process 800 isstarted, the computer control system sends a signal to the roughing pumpcontroller for the load lock 701 which, as shown in step 804, sends asignal to open the roughing pump load lock isolation valve 702. Theroughing pump then begins to draw a vacuum in the vacuum load lockchamber 12.

As shown in step 802, the control system 206 then sends a signal to openthe load lock nitrogen purge valve 703. This begins a nitrogen purge ofthe load lock chamber 12 in order to blow any particulate that hascontaminated the external surface of the vacuum wafer carrier 10 off ofthe surface and allow its removal by the vacuum system. It also allowsremoval of any particulate that has found its way into the vacuum loadlock chamber 12 during the loading sequence.

The control system 206 then provides a pressure set point signal to theload lock pressure controller 704 which provides electrical signals tothe load lock pressure control valve 705 during this nitrogen purge asindicated by step 808.

The load lock particulate sensor 202 and particle counter 850 provide aninput signal to the computer control system corresponding to the numberof particles which it detects during this purge process as shown in step806. When the particle counter 850 detects no particles for apredetermined time period, as indicated by step 810, the control system206 sends a signal to shut the load lock nitrogen purge valve 703, asshown in step 814 and to fully open the load lock pressure control valve705, as shown in step 812, via the load lock pressure controller 704which completes the purge process.

As indicated in step 816, the control system 206 then sends a signal tothe load lock turbo pump controller 706 which opens the load lock turbopump isolation valve 707.

The turbo molecular pump continues pumping down the load lock until thevacuum in the load lock is equal to or greater than that in the vacuumwafer carrier 10. Vacuum load lock vacuum is provided as an input to thecomputer control system from load lock vacuum gage 62, as shown in step818.

After the vacuum has been sufficiently lowered the control system 206sends a signal to the vacuum wafer carrier door motor 707 to fully openthe vacuum wafer carrier door 14, as shown in step 822. The door 14normally remains open until the last wafer has completed the processingsequence.

Wafers 48 can then be moved from a wafer carrier 10 to the processchamber in any order desired via the transfer arm 28 which is controlledby the control system 208. Before the control system 206 will allow thetransfer arm 28 to move the vacuum wafer carrier door sensors 708 mustindicate that the vacuum wafer carrier door 14 is fully open. Thecontrol system 206 sends a signal to the transfer arm controller 709 tomove the wafer transfer arm 28 from its home position to a positionbeneath and in close proximity to but not touching the wafer selectedfor processing, which was input to the control system 206.

When the transfer arm 28 is positioned under the wafer, the wafer armsensor 710 sends a signal to the control system 206 which indicateswhether or not a wafer is present in that location. Wafer transfer armsensor 710 is a capacitive proximity detector. If a wafer is detected asbeing present, the control system sends a signal to the transfer armcontroller 709 which allows it to continue the transfer sequence. Thetransfer arm 28 moves vertically upward and lifts the wafer 48 off ofthe ledges 60.

The transfer arm 28, now carrying the wafer on the three pins 50, asdescribed above with reference to FIGS. 1, 3, and 4, moves horizontallyout of the vacuum wafer 10. After the transfer arm 28 has cleared thevacuum wafer carrier 10, the transfer arm controller 709 positions thetransfer arm 28 at the appropriate vertical position to be able to passthrough the isolation gate 31 (FIG. 3) and placed atop the three taperedpins 53 in the process chamber.

If desired, at some time prior to attempting to move the wafer 48through the isolation gate 31, and generally at the end of the lastprocessing sequence, the process chamber has undergone a similar pumpdown and purge process as did the load lock chamber as described above.The control system 206 sends a signal to the process chamber pressurecontroller 711 which in turn sends a signal to open the process chamberroughing pump isolation valve 712. The control system 206 then sends asignal to open the nitrogen purge valve 713 and then it sends a setpoint signal to the process chamber pressure controller 714 which inturn controls the process chamber throttle valve 715 to maintain theappropriate vacuum in the process chamber during the nitrogen purgeprocess. This purge process continues until the process particle counter208 detects no particulate for a predetermined time period as monitoredby the control system 206.

Once that condition is achieved, the control system shuts the processchamber nitrogen purge valve 713 and the process chamber processcontroller 714 shuts the process chamber isolation valve 715. Thecontrol system 206 provides a signal to the process chamber turbo pumpcontroller 716 which then opens the process chamber turbo pump isolationvalve 717. The process chamber vacuum sensor 718 provides vacuuminformation to the control system 206.

Once the vacuum indicated in the process chamber by the input signalfrom vacuum sensor 718 and the load lock vacuum as indicated by vacuumsensor 62 are less than a predetermined amount, the control system sendsa signal to the isolation gate 31 to open.

Returning now to the transfer sequence, transfer arm 28 together with 28together with wafer 48 move horizontally through the isolation gate 31and into the process chamber. The transfer arm 28 is then lowered andwafer 48 comes to rest upon the three tapered pins 53 and the processchamber. The transfer arm 28 is lowered sufficiently such that the wafertransfer arm sensor 710 should indicate that the wafer was removed fromthe arm. If the wafer transfer arm sensor 710 indicates that the wafer48 is no longer on transfer arm 28 the control system 206 sends a signalto the transfer arm controller 709 which causes the transfer arm 28 tobe removed from the process chamber through the isolation gate and backto its home position. Once that sequence is complete, the control system206 sends a signal to the bellows air cylinder (not shown) that causesits upward motion and closes the process chamber in preparation for thebeginning of the process sequence.

The control system 206 can be programmed to control any of the processoperations performed, no matter which configuration of the vacuumprocessor is used. The control system 206 can establish the desiredwafer temperature by one of several methods depending upon theconfiguration of the vacuum processor. In one case, where the vacuumprocessor utilizes a resistively heated substrate, the control system206 is provided with temperature information from the heated substratetemperature sensor 720 and provides a control signal to the heatedsubstrate temperature controller 724 which controls the heated substratepower supply 725. In another embodiment. the control system provides aninput to the radiant heat lamp power supply controller 721 whichcontrols the amount of power and the rate of change of power input tothe radiant heat lamps from the lamp power supply 722. In anotherembodiment, the control system 206 provides input to the heat exchangercontrol valves 723 which control the flow of cooling water to thesubstrate. In addition, when using a microwave plasma, the controlsystem receives microwave plasma temperature information from themicrowave plasma temperature sensor 726 and in turn sends a controlsignal to the microwave plasma power supply controller 727 whichcontrols the microwave plasma power supply 728 to achieve proper plasmatemperature.

In almost all of the processes, one or more process gases are utilizedto achieve the desired results. The control system 206 sends a signal tothe manifold valve controller 729 which can control which of themanifold valves 730 are used and, consequently which gases and how muchflow is allowed to pass through each valve.

In several embodiments, in situ ultraviolet energy is provided toenhance wafer processing. The control system 206 to the UV tuner 731 inorder to match the UV (as used herein UV is defined as ultravioletlight) chamber impedance. In addition, the control system provides asignal to the UV power supply controller 732 which in turn adjusts theUV transmitter power 733.

In some embodiments, the processor uses low power radio frequency energyto accelerate charged particles to the surface of the wafer 48. Thecontrol system 206 provides inputs to an radio frequency tuner 734 sothat the impedance of the transmitter can be matched to the impedance ofthe RF (as used herein RF is defined as radio frequency) electrodes inthe process chamber.

When RF energy is used for generating a plasma or heating a substrate inthe process chamber, the radio frequency temperature sensor provides asignal to the control system 206 corresponding to the temperature of theRF electrode in the process chamber. The control system provides asignal via the RF power supply controller 736 which in turn provides asignal to the RF power supply 737 that adjusts transmitter output powerto achieve proper RF electrode temperature.

When the process is complete, the control system shuts the appropriatemanifold valves 730 and shuts off the appropriate power suppliesdiscussed above.

If desired, with the processing complete, the control system 206initiates a process chamber purge cycle as was described above. Thispurge cycle can continue for a fixed period of time or until the processchamber particle counter 208 indicates 0 particles for a predeterminedtime period.

The control systems 206 then shuts the nitrogen purge valve 713 and thepump down process continues as the control system monitors thedifferential vacuum between the load lock and the process chamber. Whenthe process chamber vacuum sensor and the load lock vacuum sensor inputsignals to the control system 206 indicate that the vacuum differencebetween the two chambers is less than the predetermined amount, thecontrol system sends a signal to open process chamber by moving thebellows downward. After the process chamber is open, the control system206 sends a signal to the transfer arm controller 709 to retrieve thewafer 48 from the process chamber and place it back in the vacuum wafercarrier.

A transfer arm controller 709 causes the transfer arm 28 to movehorizontally from its home position through the isolation gate to apoint beneath the wafer 48 in the process chamber. The wafer transferarm sensor 710 will provide a signal to the control system if it sensesproximity to the wafer 48. After receipt of this signal, the transferarm 28 moves up vertically and lifts the wafer 48 off of the taperedpins 53. The transfer arm 28 then moves through the isolation gate 31into the vacuum load lock chamber 12. The transfer arm controller 709then causes the transfer arm 28 to move up or down vertically to thevertical position of the slot from which the wafer was originally taken.

Once the transfer arm 28 is at the appropriate vertical position, itmoves horizontally into the vacuum wafer carrier 10. At this point, thewafer 48 is positioned just slightly above the ledges 60 which supportit inside the vacuum wafer carrier 10. The transfer arm controller 709then directs transfer arm 28 to move down vertically to a point whichallows the wafer to rest on the ledges 60. The transfer arm 28 continuesits downward motion. and then stops at a predetermined location beneaththe wafer 48. The control system then samples the wafer transfer armsensor 710 to see if the wafer is any longer in proximity to thetransfer arm 28. If it is not, the transfer arm is moved horizontallyout of the vacuum wafer carrier to its home position. The transfer armcan then be moved to any other wafer in the vacuum wafer carrier andbegin the process of extracting it from the wafer carrier and processingit and replacing it. This evolution can be repeated for whichever wafersthe the system 206, as programmed desires regardless of their positionin the carrier.

In an optional embodiment, for processes that require low humidity incombination with a high vacuum, the vacuum processor may utilizecryogenic vacuum pumps. These cryogenic pumps are utilized in a mannersimilar to that utilized for the turbo molecular pumps as describedabove. Their associated controllers are shown in FIG. 31 as load lockcontroller 737 and process chamber cryopump controller 738. Thesecontrollers control the load lock cryopump isolation valve 739 and theprocess chamber cryopump isolation valve 740 respectively. The cryopumpis utilized to remove moisture from the gas present in the chamber. Thisis useful for process related to HgCdTe.

When all of the wafers have completed being processed and have beenplaced back in the vacuum wafer carrier, the control system signals thevacuum wafer door motor 707 to close the door 14. The control system 206then checks the vacuum wafer carrier door sensors 708 to verify that thedoor 14 is in fact shut. The control system then shuts the load lockroughing pump isolation valve 702 load lock turbo molecular pumpisolation valve 717 or load lock cryogenic pump isolation valve 739using the corresponding load lock controllers 701, 706 and 737. Inaddition, the control system shuts the process chamber roughing pumpisolation valve turbo molecular pump isolation valve or cryogenic pumpisolation valve via the appropriate process chamber controller 711, 716and 738. It also shuts the isolation gate 31. The control system thensends a signal to open the vent valves 741 which allow the load lockchamber 12 and the process chamber to return to atmospheric pressure.The lid 20 can then open the load lock lid and remove the vacuum wafercarrier 10.

Referring to FIG. 32, a process module 1300 is shown. This processmodule has remote and in situ plasma. The wafer carrier 10, an arm (likearm 28) and chamber 12 are utilized to transfer the wafer 48 the carrier10 to the process module 1300 is shown with a gas distributor 1302attached to a gas distribution ring 1304 which is located in the upperpart of top process chamber 1306. The gas distributor 1304 supplies thegas for the in situ plasma through the ring 1304. The ring 1304 isarranged about the vertical axis of the chamber 1306. The exits fromring 1304 through a plurality of openings 1310 in the bottom of ring1304. The vertical walls of chamber 1306 can be made of quartz and forma cylinder about the vertical axis of chamber 1306. The bottom ofchamber 1306 is an electrode 1312. The top of chamber 1306 in the closedposition (as shown in FIG. 31) is an electrode 1314. A heat exchanger(not shown) can be provided for electrode 1314, if desired, for example,to maintain an ambient temperature of, for example, 25 degrees C.

The chamber 1306 is opened and closed by a bellows 1316. The bellows1316 moves the vertical walls of chamber 1306 upward and into contactwith the electrode 1314 or an adjacent portion of module 1300. A seal(not shown) can be provided at the location where the vertical wall ofchamber 1306 comes into contact. The bellows moves the chamber 1306upward to close the chamber and downward to open the chamber. In theopen position the arm can transfer the wafer 48 from the carrier throughchamber 12 and into the chamber 1306 onto fingers or pins 1320. Thesefingers 1320 are similar fingers 214 (FIG. 12) and pins 53 (FIG. 3).When the chamber 1306 is closed, the fingers 1320 move upward to placethe wafer 48 into contact with electrode 1314.

The remote plasma is supplied into the bottom of chamber 1306 along thevertical axis through a pipe 1322. Pipe 1322 extends from a remoteplasma generator 1326 and through electrode 1312 into chamber 1306. Thepipe 1322 has a slip fit 1328 with electrode 1312 to accommodate a thevertical movement of chamber 1306 including the electrode 1312. Belowelectrode 1312 is located a chamber 1330 which is connected to pump 1332and valve 1334. Thus a generally downward flow of gas through chambers1306 and 1330 is provided. The in situ plasma is provided by theapplication of appropriate voltages between electrodes 1312 and 1314.The voltage would be RF to provide the desired excitation to the gas inchamber 1306. Pump 1332 and valve 1334 provide the desired vacuum withinchamber 1306. This the remote plasma from generator 1326 and the in situplasma generated within the chamber 1306 are joined in acting on face54. The distributor 1302 also has a slip fit with electrode 1312.Distributor 1302 extends along the vertical wall of chamber 1306. Theprocess module 1300 is adapted to perform various processes.

One process which has been successfully used with the process moduleshaving both remote and in situ plasma is etching of silicon dopedaluminum, for example, Aluminum doped with 1% of silicon. A synergisticetch rate enhancement of more than double the sum of their individualetch rates was obtained for combined microwave and RF etching under thefollowing conditions: gas flows were 80 sccm BCl₃ plus 20 sccm Cl₂ plus1000 sccm He, at 1 Torr total pressure, 225 W RF Power (applied togenerate a plasma near the face of the wafer) at a frequency of 13.56MHz and 400 W microwave power at a frequency of 2450 MHz. Thetemperature used was an ambient temperature of about 25 degrees C. Theseresults were obtained even though they are based on etch rates whichwere not very high since the flows had not been optimized for theparticular conditions used, but they do show the synergistic advantageof combining these two effects. The gas mixture can all be introducedfrom pipe 1322 into chamber 1306 or a part of the gas mixture includingother gas not mentioned above, can be introduced through ring 1304.Further, a source of hydrocarbon, for example, methane could introducedthrough ring 1304 or the methane could be a part of the remotelygenerated plasma.

Another process useful with process module 1300 is for the deposition ofPolysilicon. A gas mixture of an inert gas and a source of silicon, forexample, SiH₄ and/or Si2H6 is used with remote plasma and in situ plasmato produce improved deposition rate over the sum of the rates of in situand remote plasmas used separately. As an example, the RF power is 100watts in the process chamber at an 13.56 MHz and the remote plasmagenerator is operating at 400 watts at 2450 MHz. The gases are Helium at1000 sccm and SiH₄ at 50 sccm. Argon is another example of an inert gaswhich can be used. The pressure can be 1 Torr and the temperature 25degrees C. The SiH₄ is introduced into the process chamber through ring1304 and remaining gas passes through the generator 1326. These resultswere obtained even though they had not been optimized for the particularconditions used, but they do show the synergistic advantage of combiningthese two effects. Surface damage can be reduced by increasing thepressure to greater than 1 Torr. This process results in improvedresults because of a synergistic effect between the remote and in situplasmas. The surface damage is minimized while the deposition rate isimproved. The remote and in situ plasmas can be separately controlled.This process can be used with silicon, GaAs, and HgCdTe substrates.

Another process useful with process module 1300 is for the deposition ofsilicon oxide. A gas mixture of Helium, O₂, and SiH₄ is used with remoteplasma and in situ plasma to produce improved deposition rate over thesum of the rates of in situ and remote plasmas used separately. As anexample, the RF power is 100 watts in the process chamber at an 13.56MHz and the remote plasma generator is operating at 400 watts at 2450MHz. The gases are Helium at 1000 sccm, O₂ at 100 sccm, and SiH₄ at 50sccm. The pressure can be 1 Torr and the temperature 25 degrees C. TheSiH₄ is introduced into the process chamber through ring 1304 andremaining gas passes through the generator 1326. Surface damage can bereduced by increasing the pressure to greater than 1 Torr. TheTemperature can be within the range of 25 to 400 degrees C. This processresults in improved results because of a synergistic effect between theremote and in situ plasmas. These results were obtained even though theyhad not been optimized for the particular conditions used, but they doshow the synergistic advantage of combining these two effects. Thesurface damage is minimized while the deposition rate is improved. Theremote and in situ plasmas can be separately controlled. This processcan be used with silicon, GaAs, and HgCdTe substrates.

Another process useful with process module 1300 is for the deposition ofsilicon nitride. A gas mixture of Helium, one of a group of N₂ and NH₃,and one of a group SiH₄ or SiH₂ Cl₂ is used with remote plasma and insitu plasma to produce improved deposition rate over the sum of therates of in situ and remote plasmas used separately. As an example, theRF power is 100 watts in the process chamber at an 13.56 MHz and theremote plasma generator is operating at 400 watts at 2450 MHz. The gasesused were Helium at 1000 sccm, one of a group of N₂ and NH₃ at 100 sccm,and one of a group SiH₄ or SiH₂ Cl₂ at 50 sccm. The pressure can be 1Torr and the temperature 25 degrees C. The SiH₄ or SiH₂ Cl₂ isintroduced into the process chamber through ring 1304 and remaining gaspasses through the generator 1326. Surface damage can be reduced byincreasing the pressure to greater than 1 Torr. The Temperature can bewithin the range of 25 to 400 degrees C. This process results inimproved results because of a synergistic effect between the remote andin situ plasmas. These results were obtained even though they had notbeen optimized for the particular conditions used, but they do show thesynergistic advantage of combining these two effects. The surface damageis minimized while the deposition rate is improved. The remote and insitu plasmas can be separately controlled. This process can be used withsilicon, GaAs, and HgCdTe substrates.

Another process useful with process module 1300 is for the etch of GaAs.A gas mixture of Helium, CH₄ , and one of a group of CF₄ or F₂ is usedwith remote plasma and in situ plasma to produce improved etch rate overthe sum of the rates of in situ and remote plasmas used separately. Asan example, the RF power is 100 watts in the process chamber at an 13.56MHz and the remote plasma generator is operating at 400 watts at 2450MHz. The gases used were Helium at 1000 sccm, CH₄ at 250 sccm, and CF₄or F₂ at 100 sccm. The pressure can be 1 Torr and the temperature 25degrees C. The CH₄ is introduced into the process chamber through ring1304 and remaining gas passes through the generator 1326. This processresults in improved results because of a synergistic effect between theremote and in situ plasmas. These results were obtained even though theyhad not been optimized for the particular conditions used, but they doshow the synergistic advantage of combining these two effects. Thesurface damage is minimized while the etch rate is improved. The remoteand in situ plasmas can be separately controlled. The resultant etch ispartially anisotropic. The level of anisotropy can be controlled by therelative RF plasma and microwave power levels, as well as the pressure.

Another process useful with process module 1300 is for the etch of ZnSor HgCdTe, which form at least a part of a wafer. A gas mixture of asource of atomic fluorine mixed with a inert carrier such as Helium isutilized to generate a remote plasma. An in situ plasma is generatedfrom at least the products of the remote plasma and an alkyl-bearingspecies. The powers used to generate the remote plasma and in situplasma are separately controlled to produce improved etch rates. Theremote and in situ plasmas produce an etch rate which is greater thanthe sum of the rates of in situ and remote plasmas used separately.Relative low power RF is used to generate an in situ plasma inconjunction with the remote plasma to provide an partially anisotropicetch with a relative high etch rate. Since the remote plasma and in situplasma can be separately controlled, improved profile control and etchselectivities can be achieved. An in situ descum can be performed beforethe etch and a post-etch ashing utilizing a remote plasma formed from asource of oxygen. The alkyl-bearing process can be, for example,methane, ethane, mehtylfouoride, methylchlorides, methyliodide, ormethylbromide. The source of atomic fluorine can be, for example,fluorine, CF₄, SF₆, NF₃, C₂ F₆ or any other gaseous fluorine compoundwhich releases its fluorine atoms in the presence of a plasma. The powerused can be, for example, 250 watts or less for the RF and 400 watts forthe MW. The flow rates can be 100 sccm for CF₄, 125 sccm for CH₄, and1000 sccm for Helium. The pressure can be, for example, 0.8 Torr. Thesurface damage is minimized while the etch rate is improved. The remoteand in situ plasmas can be separately controlled. The resultant etch ispartially anisotropic. The level of anisotropy can be controlled by therelative RF plasma and microwave power levels, as well as the pressure.

Another process useful with process module 1300 is for the ashing ofphotoresist. A gas mixture of Oxygen and an ashing enhancement gas, forexample, one or more of the group of CF₄, CHF₃, H₂, H₂ O, HCl, HBr, Cl₂,and N₂ O, is used with remote plasma and in situ plasma to produceimproved ashing rate over the sum of the rates of in situ and remoteplasmas used separately. As an example, the RF power is 225 watts in theprocess chamber at an 13.56 MHz and the remote plasma generator isoperating at 400 watts at 2450 MHz. The gases used were CF₄ at 43 sccmand Oxygen at 996 sccm. The pressure can be 0.63 Torr and thetemperature 25 degrees C. All of the gas can be passed through theremote plasma generator 1326. This process results in improved resultsbecause of a synergistic effect between the remote and in situ plasmas.These results were obtained even though they had not been optimized forthe particular conditions used, but they do show the synergisticadvantage of combining these two effects. The surface damage isminimized while the ashing rate is improved. The remote and in situplasmas can be separately controlled. The resultant ashing is partiallyanisotropic. The level of anisotropy can be controlled by the relativeRF plasma and microwave power levels, as well as the pressure.

Another process useful with process module 1300 is for the etch ofSilicon Nitride. A source of Fluorine and Helium were used with remoteplasma and in situ plasma to produce improved etch rate over the sum ofthe rates of in situ and remote plasmas used separately. As an example,the RF power is 225 watts in the process chamber at an 13.56 MHz and theremote plasma generator is operating at 400 watts at 2450 MHz. The gasesused were fluorine gas source, for example, CF₄ at 200 sccm and Heliumat 1000 sccm. Other sources of Fluorine can be F₂, CHF₃, C₂ F₆, SF₆, orF₃, singly or in any combination with CF₄. The pressure can be 0.7 Torrand the temperature 25 degrees C. This process results in improvedresults because of a synergistic effect between the remote and in situplasmas. These results were obtained even though they had not beenoptimized for the particular conditions used, but they do show thesynergistic advantage of combining these two effects. The surface damageis minimized while the etch rate is improved. The remote and in situplasmas can be separately controlled. The resultant etch is partiallyanisotropic. The level of anisotropy can be controlled by the relativeRF plasma and microwave power levels, as well as the pressure.

A further process useful with process module 1300 is for the etch ofpolysilicon. A source of Fluorine and Helium were used with remoteplasma and in situ plasma to produce improved etch rates of twice thesum of the remote and in situ plasmas alone. As an example, the RF poweris 225 watts in the process chamber at an 13.56 MHz and the remoteplasma generator is operating at 400 watts at 2450 MHz. The gases usedwere fluorine gas source, for example, CF₄ at 200 sccm and Helium at1000 sccm. Other sources of Fluorine can be F₂, CHF₃, C₂ F₆, SF₆, or NF₃singly or in any combination with CF₄. The pressure can be 0.7 Torr andthe temperature 25 degrees C. This process results in improved resultsbecause of a synergistic effect between the remote and in situ plasmas.These results were obtained even though they had not been optimized forthe particular conditions used, but they do show the synergisticadvantage of combining these two effects. The surface damage isminimized while the etch rate is improved. The remote and in situplasmas can be separately controlled. The resultant etch of thepolysilicon is partially anisotropic. The level of anisotropy can becontrolled by the relative RF plasma and microwave power levels, as wellas the pressure.

An other process which utilizes remote and in situ plasmas in theetching of copper doped aluminum films. The process is carried out in,for example, module 1300 or module 680 of FIG. 24. A source of Chlorine,which can be, for example, Cl₂, CCl₄, or SiCl₄, a source of hydrocarbon,for example, CH₄, and BCl₃ are used. The hydrocarbon can be omitted buta line width loss will occur. As an example, the RF power appliedbetween the electrodes within the process chamber can be about 250 wattsat 13.5 MHz. The remote plasma generator can be power at 400 watts witha frequency of 2450 MHz. The pressure with the process chamber, forexample, chamber 1306 (FIG. 31) can be 0.15 Torr. The temperature withinthe process chamber can be at an ambient temperature, for example, about25 degrees C. The gases used can be BCl₃ at 80 sccm, Cl₂ (chlorine) at10 sccm, and a hydrocarbon source, for example, CH₄ (methane) at 5 sccm.These results were obtained even though they are based on etch rateswhich were not very high since the flows had not been optimized for theparticular conditions used, but they do show the synergistic advantageof combining these two effects. The gas from the gas distributor 1302and the pipe 1322 can be the same or different as desired. This processallows the resultant etched surfaces to have reduced residues, forexample, Copper Chloride. The etch is enhanced by the use of both remoteand in situ plasma. This allows lower RF power to be used which reducessurface damage and maintains the integrity of the photoresist. Thepressure should be from less than slightly above 1 Torr to less than oneTorr.

Another useful process is an overetch of a tungsten material (a layer)to achieve selectivity to silicon dioxide and the desired anisotropy. Asource of Fluorine, which can be, for example, CF₄, C₂ F₆, HF, F₂, NF₃,or SF₆, a source of hydrocarbon, for example, CH₄, and HBr are used. Thehydrocarbon and HBr can be omitted but an improved etch is provided ifthey are present. The hydrocarbon performs a side wall passivant duringthe etch which reduces the line width loss. As an example, first, thebulk of the tungsten layer is etched using, for example, one of thetungsten etch processes discussed herein. After this step, the etchingcontinues utilizing remote and in situ plasma under the followingconditions as an example. The RF power is 50 watts in the processchamber at an appropriate frequency and the remote plasma generator isoperating at 400. The gases can be a fluorine gas source, for example,SF₆, at 40 sccm, a bromine source, for example, HBr at 13 sccm, and ahydrocarbon source, for example, CH₄ (methane) at 5 sccm. The pressurecan be 0.13 Torr and the temperature 25 degrees C. This process resultsin improved results because of a synergistic effect between the remoteand in situ plasmas which provides an increased selectivity to silicondioxide and photoresist. The etch is also improved by allowing theseparate adjustment of microwave (MW) and radio frequency (RF) powerduring the plasma generation. The pressure should be from about 0.1 Torrto about 5 Torr.

It has been found that a combination of a hydrocarbon with a brominesource provides a very potent passivating chemistry for fluorine-basedetches. For example, one embodiment which has been successfullydemonstrated is as follows: The starting structure included a thin filmof tungsten. Initial gas flows included 50 sccm of SF₆, 5 sccm of CH₄,and 15 sccm of HBr, at a total pressure of 250 milliTorr and an appliedRF power level of 500 Watts. After the pattern had begun to clear, anadditional flow of 20 sccm of WF₆ was added, as will be furtherdiscussed below. The resulting structure showed nearly vertical etchedsidewalls, only slight linewidth erosion, and excellent selectivity toresist.

By increasing the fraction of CH₄ and also that of the bromine source,even more robust passivant action can be achieved. The followingconditions produce were found, for example, to produce zero linewidtherosion: 40 sccm of SF₆, 15 sccm of CF₄, and 25 sccm of HBr, at a totalpressure of 470 milliTorr and an applied RF power level of 400 Watts.The use of relatively high total pressure assists in maintaininguniformity.

If the rate of passivant deposition is increased still further, negativeetch bias can be achieved. In a sample embodiment, a thin film oftungsten was etched using the following initial gas flows: 50 sccm ofSF₆, 18 sccm of CF₄, and 25 sccm of HBr, at a total pressure of 470milliTorr and an applied RF power level of 400 Watts. The resist patternused had 2.7 micron minimum pitch (1.7 micron minimum line width and 1micron minimum space width). The use of this chemistry was found toproduce finally etched space widths of 0.6 to 0.7 microns. Thus, thischemistry provided a "negative etch bias" of approximately 0.15-0.2micron. As an upper limit, further experiments demonstrated thatincreasing the flow of methane to 21 sccm. without changing the otherconditions, shut down the etch entirely, i.e. the tungsten etch ratewent to zero.

It has also been discovered that this class of passivating chemistriesprovides a highly anisotropic silicon etch. One specific sampleembodiment, which was successfully demonstrated by experiment, used anetch chemistry as follows: Initial gas flows included 50 sccm of SF₆, 5sccm of CH₄, and 15 sccm of HBr, at a total pressure of 250 milliTorrand an applied RF power level of 500 Watts.

These conditions etched 3 microns deep into silicon in 25 seconds, andproduced an approximately vertical silicon sidewall while maintainingexcellent selectivity to resist. However, these etch conditions are notparticularly selective to oxide. Thus, this etching chemistry isextremely useful for etching trenches. The advantages of trenches indevice structures have long been recognized, but they have usually beenfabricated by low-pressure etching conditions which are slow and areprone to produce very undesirable etching artifacts such as retrogradebowing, grooving, or asperities on the bottom of the trench. It is alsoan advantage of the avoiding these difficulties of low-pressureprocessing.

Another, alternative, family of chemistries for fluoro-etching uses afeed gas mixture which includes a fluorine source such as SF₆) plus abromine source, such as HBr, plus a very weak oxygen source (e.g.,carbon monoxide). This chemistry provides anisotropic high ratefluoro-etching with good selectivity to photoresist.

A sample embodiment of the process discussed has been successfullydemonstrated as follows: The starting structure included a thin film oftungsten covered by a patterned layer of developed organic photoresist.Initial gas flows included 25 sccm of SF₆, 25 sccm of HBr, and 40 sccmof CO, at a total pressure of 300 milliTorr and an applied RF powerlevel of 175 Watts. During the overetch period an additional flow of 20sccm of WF₆ is usefully added. The resulting structure showed steeplysloped sidewalls, only moderate linewidth erosion, and approximately 2to 1 selectivity over photoresist.

This chemistry could be modified by substituting another weak oxygensource for the carbon monoxide. That is, weak oxygen sources such as N₂O or CO₂ could be used instead. In fact, it would even be possible toderive some benefit by using an extremely small flow (less than onesccm) of O₂ in place of the CO, but such very small flows are difficultto control reproducibly with conventional semiconductor manufacturingequipment.

Another, alternative, family of chemistries for fluoro-etching uses afeed gas mixture which includes a fluorine source (such as SF₆) plus afluorosilane (e.g., SiF₄), plus a bromine source (such as HBr), plus aweak oxygen source such as carbon monoxide. This chemistry providesanisotropic high rate fluoro-etching with good selectivity tophotoresist.

A sample embodiment of this process has been successfully demonstratedas follows: The starting structure included a thin film of tungsten,covered by a patterned and developed layer of organic photoresistmaterial. Initial gas flows included 25 sccm of SiF₄, 25 sccm of SF₆, 25sccm of HBr, and 30 sccm of CO, at a total pressure of 350 milliTorr andan applied RF power level of 175 Watts. During the overetch period anadditional flow of 30 sccm of WF₆ is added to the other flows described,to avoid resist erosion. The resulting structure showed nearly verticaletched sidewalls, only slight linewidth erosion, and approximately 3 to1 selectivity to the photoresist.

A another process which is adapted for use with process module 1300 is alow pressure silicon nitride etch. This etch utilizes a remote plasmagas mixture of SF₆ flowing at 100 sccm and He flowing at 5000 sccm. Thesubstrate has a temperature of 25 degrees C. RF plasma was notgenerated. The etch rate of the silicon nitride was 37 angstroms perminute. The silicon dioxide was observed not to have etched. An additionsource of Fluorine could be used such as F₂, CF₄, or C₂ F₆. Theseadditional sources may reduce the selectivity of the etch to siliconoxide. The etch rate can be increase by the additional use of RF in situplasma. This process is also useful for GaAs and HgCdTe processing.

In another process, after one of the tungsten etches described above hasetched most of the tungsten film the present process is utilized toprovide an etch which is both anisotropic and selective to silicondioxide and photoresist by utilizing both remote and in situ plasmas.The gas mixture used was comprised of SF₆ at 40 sccm, HBr at 13 sccm,and a source of hydrocarbons, for example, CH₄ (methane) at 5 sccm. Thepressure and temperature used were 0.13 Torr and 25 degrees (ambient)C., respectively. The RF and W power used to produce the in situ andremote plasmas were 40 and 400 watts, respectively. The in situ andremote plasmas produce a synergistic effect which results in improvedetch characteristics, including selectivity and anisotropy. Thisincludes the separate control of the generation of the remote and insitu plasmas.

In FIG. 33, a wafer carrier 10 is shown with its door 14 is open.Transfer arm 28 is shown transferring a wafer 48 between carrier 10 anda platform 1500. The arm 28 acts as discussed above in connection withFIGS. 1, 3, and 4. The arm 28 is located within a load lock chamber1502, which is similar to chamber 12. The platform 1500 can be hinged torotate along its bottom side from vertical position to the horizontalposition shown in FIG. 33. The platform would form a seal with thechamber 1502. This would allow a vacuum to be formed by pump 1504 withinchamber 1502. Alternatively, a door or isolation gate (not shown) can beincluded to provide an sealable opening through chamber 1502 for arm toextend to platform 1500. The carrier 10 which contains wafers in vacuumis placed into chamber 1502. The chamber 1502 is pumped down to thedesired vacuum by pump 1504. A particle counter, similar to counter 850,can be used to monitor the particles within chamber 1502. The door 14would not be opened until the desired particle conditions are obtainedas discussed herein with reference to the various Figures includingFIGS. 11 and 31. A purge can be conducted if desired. Once the desiredvacuum is established the door 14 is opened. The chamber 1502 is thenvented to ambient pressure by introducing a clean gas, for example, N₂(nitrogen). The platform, door, or isolation gate is opened. The arm 28can reach into carrier 10 under a wafer 48. The arm is raise slightly tolift the wafer. This is the leftmost position in FIG. 33. The arm is themoved out through opening 1510 in chamber 1502. The wafer 48 contacts atits circumference 49 three pins 50 (only two are shown in FIG. 33). Thewafer 48 is shown with its face 54. which is to have devices orintegrated circuits constructed therein and/or thereon. In the rightmostposition in FIG. 33, arm 28 is shown positioned over platform 1500. Theplatform 1500 has three pins 1512 (only two are shown in FIG. 33)similar to pins 53 in FIGS. 1, 3, and 4. The arm is lower slightly toplace wafer 48 onto the pins 1512.

The wafer 48 can then be picked up by another transport mechanism 1520.The transport mechanism 1520 can be another transport arm similar to arm28 or appropriate mechanism. All of the wafers could be transferred tothe platform 1500 one wafer at a time. In the alternative, one wafercould be processed within a non-vacuum processing system (not shown)after transport thereto by mechanism 1520, returned to platform 1500,and then to carrier 10. The next wafer could then be transferred toplatform 1500 form carrier 10. When it desired to close carrier 10, itis necessary to close the platform, door, or isolation gate. Vacuum isapplied to chamber 1502 and the chamber is again purged using a gas, forexample, N₂. The particular counter can be monitored by computer controlsystem 206 and the door 14 closed after the desired conditions are met.The wafers can be transferred by arm 28 face down as described herein.The computer control system 206 (FIGS. 10 and 31) would provide thenecessary control to arm 28 and chamber 1502.

The general configuration shown in FIG. 34 is similar to that in FIG.33. However, the wafers, for example, wafer 48 are not placed on aplatform but rather are placed into a non-vacuum carrier 1540 by arm 28.One or more wafers (or all) can be placed into carrier 1540. The carrier1540 is located on a support, for example, extending from chamber 1502.A transport mechanism 1542, which can be a robotic arm, has a hand 1544and a claw 1546 which is adapted to grip and move carrier 1540 to thenon-vacuum processing equipment (not shown) which could be, for example,for photolithography. The carrier 1540 can also be moved and replaced byother means, for example, manually. The pump down sequence and thegeneral operation has been discussed above in connection with FIG. 33.

The transfer mechanisms in FIGS. 35 and 36 are generally similar tothose shown in FIGS. 33 and 34, respectively. A wafer carrier 10 isshown with its door 14 is open. A platform 1600 is shown receiving awafer 48 from arm 28. The arm 28 acts as discussed above in connectionwith FIGS. 1, 3, and 4. The arm 28 is located within a load lock chamber1602, which is similar to chamber 12 (shown FIGS. 1, 3 and 4). Theplatform 1600 is similar to platform 1500 shown FIG. 33 and rotatesalong its bottom side from vertical position to the horizontal positionshown in FIG. 35. The platform would form a seal with the chamber 1602.This would allow a vacuum to be formed by pump 1604 within chamber 1602.Alternatively, a door or isolation gate (not shown) can included toprovide an sealable opening through chamber 1602 for arm to extend toplatform 1600. The carrier 10 which contains wafers in vacuum is placedinto chamber 1602. The chamber 1602 is pumped down to the desired vacuumby pump 1604. A particle counter, similar to counter 850, can be used tomonitor the particles within chamber 1602. The door 14 would not beopened until the desired particle conditions are obtained as discussedherein with reference to the various Figures including FIGS. 11 and 31.Once the desired vacuum is established the door 14 is opened. Thechamber 1602 can be purged by introducing a clean gas, for example, N₂(nitrogen) as discussed above in connection with the chamber 12 and theprocess modules. The platform, door, or isolation gate is opened. Thearm 28 can reach into carrier 10 under a wafer 48. The arm is raiseslightly to lift the wafer. This is the leftmost position in FIG. 35.The arm is the moved out through opening 1610 in chamber 1602. The waferis resting on three pins 50 (only two are shown in FIG. 35). In therightmost position in FIG. 35, arm 28 is shown positioned over platform1600. The platform 1600 has three pins 1612 (only two are shown in FIG.35) similar to pins 53 in FIGS. 1, 3, and 4. The arm is lower slightlyto place wafer 48 onto the pins 1612.

The wafer 48 can then be picked up by another transport mechanism 1620which is located within vacuum enclosure 1621. This enclosure 1621 isnot similar to the standardized modules shown herein, which havebasically the same shape, transfer, and closure mechanisms. Thetransport mechanism 1620 can be another transport arm similar to arm 28or appropriate mechanism. All of the wafers could be transferred to theplatform 1600 one wafer at a time. In the alternative, one wafer couldbe processed within the non-standard processing module (not shown exceptfor chamber 1621) under vacuum after transport by mechanism 1620,returned to platform 1600, and then to carrier 10. The next wafer couldthen be transferred to platform 1600 from carrier 10. When it desired toclose carrier 10, it is necessary to close the platform, door, orisolation gate. Vacuum is applied to chamber 1602 and the chamber isagain purged using a gas, for example, N₂. The particular counter can bemonitored by computer control system 206 and the door 14 closed afterthe desired conditions are met. The wafers can be transferred by arm 28face down as described herein. The computer control system 206 (FIGS. 10and 31) would provide the necessary control to arm 28 and chamber 1602.

The general configuration shown in FIG. 36 is similar to that in FIG.35. However, the wafers, for example, wafer 48 are not placed on aplatform but rather are placed into a non sealable carrier 1640 by arm28. One or more wafers (or all) can be placed into carrier 1640. Atransport mechanism 1642 has a hand 1644 and a claw 1646 which isadapted to grip and move carrier 1640 to the processing equipment, whichis not of the standardized module type as shown herein. The carrier 1640can also be moved and replaced by other means, for example, manually.The pump down sequence and the general operation has been discussedabove in connection with FIG. 35.

A process module 2000 is shown in FIG. 37. Many of the components ofprocess module 2000 as similar to the components of other modulesdiscussed above. The carrier 10 and chamber 12 operate as discussedabove in connection with FIGS. 1, 3, and 4 above. The wafer 48 is shownis with in carrier 10 at its leftmost position and in transit withinchamber 12 in its middle position. The type of particle controldiscussed above in connection with FIG. 11 can be used with module 2000and the other modules disclosed herein. Wafer 48 in its rightmostposition is disposed within a process chamber 2002. A remote plasmagenerator 2010 generates a remote plasma using microwave energy from thegas mixture supplied through pipe 2012. The feed 250 provides the remoteplasma from generator 2010 to chamber 2002. Pipes 2020 and 2022 areconnected through a vacuum connection to ultraviolet space 2024 andchamber 2002, respectively. Pipes 2020 and 2022 are connected to gasdistribution rings 2026 and 2028, respectively. Space 2024 is locatedbelow chamber 2002. A quartz baffle 2030 separates spaces 2024 fromchamber 2002. The feed 250 has a slip-fit with quartz baffle 2030. Thequartz baffle 2030 has a basic H-shape in cross-section with feed 250passing through the center of the crossbar. Ring 2026 is located withspace 2024 and ring 2028 is located within chamber 2002.

The module 2000 has a pump 2040 and a valve 2042. The quartz baffleforms a part of the sides and bottom of chamber 2002. The quartz baffleis show in FIG. 37 in its upper or closed position. The bellows 2032provides the vertical movement for quartz baffle 2030. A heat module2050 is located above chamber 2002. A transparent plate 2052 separatesheating module 2050 and chamber 2002. The heat from heating module 2050is radiantly coupled to wafer 48 through plate 2052. The plate 2052forms the top of chamber 2002 in the closed position as shown in FIG.37. The wafer 48 with its face 54 downward is located just below plate2052.

The heating module 2050 is provided with two rings 2060 and 2062 ofheating elements. Ring 2060 is located outside the ring 2062. Each ringis comprised of a plurality of heat lamps, for example, 24 in ring 2060and 12 in ring 2062. The rings are separately controllable. A reflector2070 is adapted to directed the heat from the rings 2060 and 2062through plate 2052. The heating module 2050 will be discussed in detailin connection with FIGS. 38, 39, and 40. FIGS. 38, 39, and 40 showmodifications to the basic process module 2000 shown in FIG. 37.Therefore, the discussion of FIGS. 38, 39, and 40 will be primarilyfocused on the differences between the Figures.

FIG. 38 show process module 2000 with the heating module 2050 and twolamps 2100 and 2102 from ring 2060 and two lamps 2104 and 2106 from ring2062. Reflector 2070 is also shown in FIG. 38. The power suppliesconnect to the lamps for ring 2060 and ring 2062 are separatelycontrolled by computer control system 206. This allows a greater varietyof heating configurations to be available as required. A heater space2110 is located between the the rings 2060 and 2062 and a portion ofreflector 2070, and the plate 2052. The heater space is located aboveand extends laterally beyond plate 2052. The feed 250 and rings 2026 and2028 are located as discussed above in connection with FIG. 37. Quartzbaffle 2030 is shown in cross-section. A vertical axis 2120 is shownextending through a central portion of module 2000. Feed 250, baffle2030, rings 2026 and 2028, plate 2052, reflector 2070, and rings 2100and 2102 are concentric about axis 2120. The baffle 2030 and rings 2026and 2028 are moved vertically along axis 2120 by bellows 2032. Thechamber 2002 is shown in its closed position with the quartz cylinder2210 against fixed upper support 2212. A seal 2214 as discussed hereincan be provided to provide the necessary separation between chamber 2002and the remainder of the interior of module 2000. A generally downwardflow from chamber 2002 is provided by pump 2040 FIG. 37.

Two electrodes 2230 and 2232 provide the vertical walls for space 2024.Electrodes 2230 and 2232 are cylinders concentric with axis 2120.Electrode 2230 is disposed about electrode 2232. The electrodes 2230 and2232 provide the necessary power to excite the gas introduced into space2024 from ring 2026, as discussed above in connection with the otherprocess modules which have ultraviolet light generation capability.Electrical contact to electrodes 2230 and 2232 is through conductors2240 and 2242. The power supplied would be from a power supplycontrolled by computer control system 206 as described above. A sensorarray 2244 extends upward along the exterior wall of baffle 2030, overthe top of the baffle, and horizontally into chamber 2002. A pluralityof temperature sensors 2246 (three are shown in FIGS. 38, 39, and 40although the number can vary) are disposed on the horizontal portion ofarray 2244. The sensors 2246 are located just below the face 54 of thewafer 48 to measure the temperature at the area where they are disposed.A opening 2250 in plate 2052 extends from the circumference of plate2052 horizontally to the center and then downward to the lower surfaceof plate 2052. Opening 2250 will be discussed in detail herebelow.Fingers 2260 (only one of three fingers in shown in FIG. 38) hold thewafer 48 against plate 2052 and are similar to the fingers 53. The array2244 can be utilized with the other heating modules shown herein, forexample, that shown in FIGS. 18 and 19.

The reflector 2070 has a portion with a conic frustum with a flat tip2272 with a cone shaped surface 2274 extending upward and away from theflat tip 2272. The flat tip 2272. The center of flat tip 2272 iscoincident with axis 2120. The surfaces of the reflector 2070 will nowbe discussed and it should be appreciated that they are shown incross-section in FIG. 38. Another cone shaped surface 2276 extendsupward and away from axis 2120 at greater angle than surface 2274. Fromsurface 2276, a horizontal surface 2278 extends perpendicular to axis2120 to a cone shaped surface 2280. Surface 2280 extends away fromsurface 2278 downward and outward from axis 2120 to a horizontal surface2282. The horizontal surface 2282 extends from surface 2280 outwardperpendicular to axis 2120 to another cone shaped surface 2284. Fromsurface 2282, surface 2284 extends downward and outward from axis 2120.The outward most part of surface 2284 is at approximately the samedistance along axis 2102 as tip 2272. Surfaces 2274 and 2276 meet atabout the same distance along axis 2120 as surface 2282 is located. Thetip 2272 and surfaces 2274, 2276, 2278, 2280, 2282, and 2284 form theupper portion of reflector 2070. Tip 2272 is spaced from plate 2052.

The lower portion of reflector 2070 has a cylindrical surface 2290 whichis concentric about axis 2120. The lower end of surface 2290 extendsbelow wafer 48 and is separated from chamber 2002 by a ring shaped foot2292 of plate 2052 which extends downward beyond wafer 48. Foot 2292extends outside the circumference of wafer 48 and is spaced therefrom.In other words, foot 2292 extends from the main body of plate 2052downward a distance along axis 2120 greater than wafer 48 as shown inFIG. 38. From surface 2290, the reflector 2070 has a cone shaped surface2300 which extends upward and away from axis 2120. A horizontal surface2302 extends outward perpendicular to axis 2120 from its connection tosurface 2300. The upper and lower portions of reflector are notconnected although each forms a continuous surface. The surface 2284 isat about the same distance along axis 2120 as surface 2274 and the heatelements of lamps 2100 and 2102. Surface 2284 can be at an angle toreflect heat from lamps 2100 and 2102 approximately parallel to surface2300 and onto the wafer with a greater concentration of the heatdirected onto the area adjacent its circumference. The heat elements oflamps 2104 and 2106 are about the same distance along axis 2120 assurfaces 2276 and 2280. The surfaces 2276 and 2280 reflect heat fromlamps 2104 and 2106 onto wafer 48 with a greater concentration of theheat from the lamps directed onto the central area of the wafer. Surface2300 can be angled to reflect heat upward and toward axis 2120 and ontosurface 2276. Surface 2302 also directs heat upward for reflectiondownward. Surface 2290 directs additional heat horizontally toward axis2120 and onto the edge. In general the surfaces and tip of reflector2070 direct and redirect heat through space 2110 to provide the maximumamount of heat onto the wafer 48. The particular reflector 2070 shownherein is only one way of implementing a reflector for heating module2050. Since the wafer 48 is against plate 2052, the upward facing faceof wafer 48 is protected during depositions.

The module 2000 is shown in FIGS. 39 and 40 along with heating module2050 and reflector 2070 are the same as those shown in FIG. 38 and willnot be discussed further. The rings 2026 and 2028, baffle 2030, plate2052, feed 250 and in general the entire configuration of the lower partof the module 2000 are approximately the same and only the modificationswill be discussed.

In FIG. 39, an electrode 2310 is located between wafer and plate 2052.The plate 2052 is conductive and can be made of, for example, graphiteor silicon. Conductor 2312 is attached to electrode 2310 near its edge.Fingers 2260 bring wafer 48 into contact with electrode 2310 when thechamber 2002 is closed as shown in FIG. 39. It should be noted that thefingers 2260 have a notch 2330 which allows the wafer to lie in thenotch with the upper ends of the fingers to rest against plate 2052 withthe wafer held against electrode 2310 (or as shown in FIG. 38, againstplate 2054. However. the pins 53 in FIGS. 1, 3, and 4 could also beused. The heat from module 2050 is directed onto electrode 2310 exceptat the circumference of wafer 48 by surface 2290 directing heat towardaxis 2120. The sensors 2246 also provide the same function of providingthe temperature of the wafer at various locations, for example, adjacentthe circumference, at about one half of the radius, and adjacent thecenter. This arrangement allows the use of in situ plasma. The RF powerwould be applied to electrode 2310 and cylindrical support 2311. Thiswould allow the RF enhanced plasma as discussed above to be utilized forthe above described processes and for chamber cleanup as describedabove.

In FIG. 40, the fingers 2260 have a deeper notch 2332 than nothc 2330which allows the tips of fingers 2260 to rest against plate 2310 whilethe wafer 48 remains spaced from plate 2310 by a space 2234. The opening2250 in plate 2052 provides a purge gas, for example, an inert gas suchas Helium and H₂ to the upward facing face of wafer 48 which preventsdeposition on that side of the wafer. The sensors 2246 perform the samefunction as in FIGS. 38 and 39. The surface 2290 of reflector 2070extends far enough down to direct heat onto the circumference of wafer48. The various modifications of module 2000 shown in FIG. 37, 38, 39,and 40 show the flexibility of the basic module concept with improvedheating at the circumference of the wafer.

Unless specifically stated otherwise above the power and frequenciesused for RF and W plasma and ultraviolet light can be widely varied, ascan the other process parameters. The term low pressure as used hereinindicates a pressure which is less than ambient pressure.

All of the process modules disclosed herein can be utilized with one ormore of the chamber 12 and arm 28 as shown in FIGS. 1, 3, 4, 5A, and 5B.Although silicon, GaAs, and HgCdTe examples are shown herein wafers madeof other materials such as germanium, etc. The wafers can be comprisedof many different configurations, for example, a single piece of crystalmaterial or small crystals located on a larger substrate. The plasmaproduced as disclosed herein will include free radicals. Although waferssuch as wafer 48 are disclosed herein other types of flat workpiecescould be used with the techniques disclosed herein.

The result of processing the wafer 48 can be electronic devices, forexample, integrated circuits or discrete semiconductor devices. Once theprocessing is completed the wafers are divided into devices. Thecircuits and devices are enclosed into packages, for example, as shownin U.S. Pat. Nos. 4,465,898 issued to Orcutt et al on Aug. 14, 1984 and3,439,238 issued to Birchler et al on Apr. 15, 1969, which areincorporated hereinto by reference. These packages are then utilized inthe construction of printed circuit boards. The printer circuits boards,which cannot operate without the packaged integrated circuits anddevices to perform their intended functions, are the required electricalcomponents within computers, photocopiers, printers, telecommunicationequipment, calculators, and all of the other electronic equipment whichare an essential ingredients of the electronic and information age. Thuselectronic equipment cannot function with the circuits and devices.

The present application describes a processing system and a number ofclasses of process stations and a number of classes of processingmethods, which respectively contain numerous additional features whichserve to provide further advantages.

It is an advantage of the present invention that it reduces damage whichcould be caused by excessive plasma bombardment.

It is an additional advantage of the present invention that it allowsoptimizing the the plasma bombardment to provide anisotropy, whileallowing the optimization of the selectivity and control of extraneousdeposition.

It is yet a further advantage of the present invention that it permitsprocesses to be operated at high throughput under low-bombardmentconditions.

It is yet another advantage of the present invention that it permits theaccomplishment of a sequence of in situ operations that include pre etchdescum, pre etch UV resist treatment, enhanced etching, post etch resistremoval, oxide removal, metal contaminant removal, organics removal, andenhanced deposition.

The present invention also advantageously allows rapid process chamberclean-up.

Having described the invention in connection with certain specificembodiments thereof, it is to be understood that further modificationsmay now suggest themselves to those skilled in the art, it is intendedto cover all such modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for processing wafers, comprising thesteps of:(a) transferring a wafer into a process chamber; (b) applying apressure to said chamber less than ambient to maintain the chamber atless than ambient (c) providing a first gas to a remote plasma chamberseparated from said chamber and producing a remote plasma; (d)generating a second plasma, separate from said first plasma, inproximity to the face of said wafer; (e) illuminating the wafer withultraviolet energy from an ultraviolet energy source within said vacuumchamber separate from the wafer; (f) flowing the remote plasma over saidwafer disposed within said chamber.